image = $0 } // 雖然下面的語法沒有出現錯誤訊息，但依然沒用SOLVED: Escaping closure captures 'inout' parameter Forums > Swift @kikashi59 Jun '21 I'm trying to get a web page, parse it and return a value extracted. id }) { return Binding ( get. How to fix "error: escaping closure captures mutating 'self' parameter. x and Swift 2. 3 Escaping closure captures mutating 'self' parameter: struct Escaping closure captures mutating 'self' parameter: struct. // This actually throws an error: Escaping closure captures mutating 'self' parameter: toastManager. Viewed 921 times 1 This question. Q&A for work. Value types like structs exist on the stack frame. 3. This is what separates a closure (which "closes over" the scope where it was created) and an anonymous function (which does not). Swift 5: O que é o 'fechamento de escape captura o parâmetro' self 'mutante' e como corrigi-lo . Teams. 0. The longer version. Using Swift. A closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. ⛔. ; class, the reference itself does not change even when you mutate its properties, because reference just points to some memory whose content is modified, but. . Basically, it's about memory management (explicit/escaping vs. Escaping closure captures non-escaping parameter 'completion' (Swift 5) 1 Capturing closures within closures: Xcode throws error: Escaping closure captures non-escaping parameterTeams. I understand that the line items. An escaping closure is like a function variable that can be performed at a later time. md","path":"proposals/0001-keywords-as-argument. This has been asked and answered before. this AF. This is where capture lists come in, which enable us to customize how a given closure captures any of the objects or values that it refers to. timeLeft)}) { A simple solution is to change Times to be a class instead of a struct. Escaping Closures. In your case you are modifying the value of self. 1. md","path":"proposals/0001-keywords-as-argument. (The history of the term "close over" is kind of obscure. global(). ' to make capture semantics explicit" 7. This means we can pass Content. Even the name UILogic , while just a name, hints that you may need to rethink your use of the MVVM architecture. Closures normally capture by reference, but it mentions in a note in the Swift Language Guide that: "As an optimization, Swift may instead capture and store a copy of a value if that value is not mutated by or outside a closure. 1. But it doesn't seem to be what you are actually doing. I am having troubles with running view methods on published property value change. id > $1. 1. But here is that even the closure is being taken as a parameter, we can use trailing closure syntax, and use code like option2?Following code produces Escaping closure captures mutating 'self' parameter error: struct Foo { @State var count = 0 init { Timer. ⛔️ escaping closure captures mutating 'self' parameter. vn team, along with other related topics such as: swift escaping closure captures ‘inout’ parameter escaping closure captures mutating ‘self’ parameter, escaping closure swift, swift inout struct, closure callback swift, mutable capture of inout parameter self is not. 1 Answer. 0. off state: private enum MyTimer { case off case on (Date, Timer) // start time, timer mutating func start. Creating a simple card game (Set) and I have a function in the model that deals X cards onto the deck. エラー文です ・Escaping closure captures mutating 'self' parameter 直訳すると「クロージャをエスケープすると、「self」パラメータの変化がキャプチャされる」となると思うのですが、何を言っているのかよくわかりません。 クロージャのescapingやキャプチャに関しては理解しているつもりです。Hi, I’m new to Swift and also to SwiftUI. But it always gives me the error: Closure cannot implicitly capture a mutating self parameterIt isn't clear to me that you need a timer for your example, but since there is a great deal of misinformation out there about how to include a Timer in a SwiftUI app, I'll demonstrate. This note summarizes the errors that occurred during the development of Swift. SwiftUI run method on view when Published view model member value changes. Unfortunately, without seeing the closure, I cannot tell you why the closure is escaping. . The introducing of @escaping or @nonEscaping for optional closures should be easily accepted. In this video I'll go through your question, provid. In this recent thread: An odd error: "Escaping closure captures mutating 'self'" - #10 by Jens, I, (well, actually @Jens), just found out that this code compiles: func test(_ callback: () -> Void) { // Compiles, no need for it to be @escaping let x = callback x() } It baffles me because I don't think we have non-escaping closure types (yet). main. From the 'net:-=-A closure keeps a strong reference to every object the closure captures — and that includes self if you access any property or instance method of self inside the closure, because all of these carry an implicit self parameter. md","path":"proposals/0001-keywords-as-argument. Stack Overflow | The World’s Largest Online Community for DevelopersIf you use a guard let, your closure captures self at the beginning of the closure. An escaping closure that refers to self needs special consideration if self refers to an instance of a class. But now I'm getting a "Escaping closure captures mutating 'self' parameter" – Dante. I use this boolean to show a view on a certain state of the view. before you use them in your code, such as self. when accessing instance properties/methods when acknowledging that you capture self strongly by using [self]. Accessing an actor's isolated state from within a SwiftUI view. 函数执行闭包（或不执行）. 4. [self] in is implicit, for. By non-escaping parameter, it means that the parameter cannot exist outside the scope of the function. Swift 5 : What's 'Escaping closure captures mutating 'self' parameter' and how to fix it 8 Escaping closure captures mutating 'self' parameter Escaping closure captures mutating 'self' parameter You’re now watching this thread. Escaping closure captures non-escaping parameter 'action' You’re now watching this thread. 1. But I can't figure out how to properly invoke withoutActuallyEscaping(_: do:). . turnON(). firestore () init () { let user =. I understand the problem with trying to modify a struct from within a closure, but I don't know what I'd need to change to be able to update the UI, based on the results from the face detection request. Jan 6, 2020 at 11:39. 229k 20 20 gold. Previous ID SR-2474 Radar None Original Reporter @karwa Type Bug Status Resolved Resolution Duplicate Environment Swift f5f6905 Additional Detail from JIRA Votes 0 Component/s Compiler Labels Bug,. If the escaping closure isn’t property released, you’ve created a strong reference cycle between self and the closure. The output is now: Counter value is 1 This finally works, and we can see the state change from the loopBreaker closure is correctly affecting the result printed in the OnDelete closure. h has been modified since the module file. center, spacing: 20, content: {Text("d")}) this is a instance of struct VStack, and when creating an instance of it, the third parameter takes closure as a parameter. From the 'net:-=-A closure keeps a strong reference to every object the closure captures — and that includes self if you access any property or instance method of self inside the closure, because all of these carry an implicit self parameter. Escaping closure captures non-escaping parameter 'completion' (Swift 5) In my project, I came across a situation when I need to use the background queue to create an AVPlayerItem (which I create in setupTrackModels function). Since such closures may be executed at a later time, they need to maintain strong references to all of. Connect and share knowledge within a single location that is structured and easy to search. This can lead to retain cycles for which I recommend reading my article Weak self and unowned self explained in Swift to better understand how values are captured. 3 Swift can change struct declared with let if using an index but not if using a loop. So at here VStack(alignment: . Binding is by definition a two-way connection. e. 上面代码会报错：“Escaping closure captures mutating 'self' parameter” 逃逸闭包不可修改 的self这个参数。 当self是结构体或枚举实例时，逃逸闭包不能捕获此self。 如果self是一个类的实例，则逃逸闭包能捕获self。 如果只是普通闭包则能捕获所有类型的self。 项目中使用. [email protected]!(characteristic. firstName = firstName. Locations. I have the following Struct that I want to initialize, and then use its method query() to mutate its result property. That's what inout does. 1. For a small application that I want to implement I’d like to stick with MVVM. Or search Stack Overflow for "closure cannot implicitly capture a mutating self parameter" (search with quotes around the message). I've been writing a simplified version of Stack using enum types: public enum Stack<Element> { case empty indirect case node (value: Element, next: Stack<Element>) public init (_ elements: Element. SwiftUI run method on view when Published view model member value changes. e. Escaping closure captures mutating 'self' parameter E não sei onde ou o que perdi nesta lição. responseDecodable(of: PeopleListM. 1 Why is Swift @escaping closure not working? 3. This broke a lot of code of mine. What's happening in your code is that your inout variable is escaping the lifetime of the function (by being captured in a closure that is then stored) – meaning that any changes to the inout. covadoc. The line that begins with let request = throws the following error: Escaping closure captures mutating 'self' parameter. 2. Since the closure can be stored and live outside the scope of the function, the struct/enum inside the closure (self) will be copied (it is a value) as a parameter of the closure. Previous ID SR-15459 Radar None Original Reporter @okla Type Bug Environment Xcode 13. . The purpose of this would be to have a convenient way to create a Binding in DetailView that was called from a NavigationLink of a List. Query() sends and fetches JSON data, then decodes it to a String. Fetch data from server swiftUI. {"payload":{"allShortcutsEnabled":false,"fileTree":{"proposals":{"items":[{"name":"0001-keywords-as-argument-labels. SPONSORED Elevate your skills from design to SwiftUI by joining Design to SwiftUI, where you'll become skilled in weaving in unique design elements that enhance both aesthetics and user experience. A closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. md","path":"proposals/0001-keywords-as-argument. 1. That way the SwiftUI runtime will manage the subscription for you, even while your view may be recreated many times. md","path":"proposals/0001-keywords-as-argument. (where I use an explicit self. The type owning your call to FirebaseRef. Rewrite your closure to ensure that it cannot return a value after the function returns. 5. append(str) modifies the parent ContentView object out of dataTask closure and that is not good for some reason. One way that a closure can escape is. Yes. 1 (13A1030d), MacOS 11. Stack Overflow | The World’s Largest Online Community for DevelopersStack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the companyStack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the companyCapturing values in a closure. The type owning your call to FirebaseRef. If you intend for it to escape. observeSingleEvent (of:with:) is most likely a value type (a struct ?), in which case a mutating context may not explicitly capture self in an @escaping closure. Escaping Closures. I understand the problem with trying to modify a struct from within a closure, but I don't know what I'd need to change to be able to update the UI, based on the results from the face detection request. init (initialValue. Type, completionHandler: @escaping (String?)->Void)Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; Labs The future of collective knowledge sharing; About the companyStack Overflow | The World’s Largest Online Community for DevelopersProtocol '. In-out parameters are used to modify parameter values. 1. Passing a non-escaping function parameter 'anotherFunc' to a call to a non-escaping function parameter can allow re-entrant modification of a variable 2. the closure that is capturing x is escaping kind or nonescaping kind. The problem with capturing mutating self in an @escaping closure in a struct is there are really only two choices in how Swift might theoretically attempt to do it. the mutated path as an inout parameter to the closure: mutating func withAppended(_ path: String, _ closure: (inout MyFilePath) -> Void) { components. game = game } func fetchUser (uid: String) { User. Forums. funkybro funkybro. I'd suggest moving asynchronous code like this to an. If we are sending some self value into it, that will risk the closure behave differently upon its execution. 0. There are several other possible errors related to closure captures being able to effectively make structs into reference types (thereby destroying any guarentees that come from being a value-type) Swift: Capture inout parameter in closures that escape the called function 45 Swift 3. This is one of the crucial differences between member func declarations and closure declarations: self has different meaning in those. Anyway if you like to use your code, then capture the self inside your mutation method like below: mutating func getUserWorkspace (base: String, completed: @escaping () -> ()) { let url = URL (string: "some url")! var request = URLRequest (url: url) var myself = self request. – vrwim. But to be sure that self exists at the moment when completionHandleris called compiler needs to copy self. Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the companyHi all. Capturing self in an escaping closure makes it easy to accidentally create a strong reference cycle. Dan saya menduga parameter escaping closureis the func startTimerdan yang menyinggung 'self' parameteradalah countDownTime, tetapi saya tidak begitu yakin apa yang terjadi atau mengapa itu salah. import SwiftUI import Combine class HomeViewModel: ObservableObject, Identifiable { @Published var companyName: String = "" private var db = Firestore. for me anyway. My data models were all structs and as such self was a struct which was being passed into the closure. You need to refer self explicitly within the escaping closure. We should disallow implicit capture of `inout` parameters; except in `@noescape` closures. " but we are using this inside the function5 Answers. Improve this question. Asking for help, clarification, or responding to other answers. S. I'm having a hard time constructing an example for such a retain cycle on the top of my head, what am I. Using a mutating function is really fighting the immutable nature of structs. Difficulty trying to use a struct to replace a cluster of stored properties in a class. 1 Answer. (Do you have some other reason for wanting to store the timer. This has been asked and answered before. – Rob エラー文です. Learn more about TeamsTeams. The type owning your call to FirebaseRef. Cannot assign to property: 'self' is immutable problem. e. Connect and share knowledge within a single location that is structured and easy to search. ・Escaping closure captures mutating 'self' parameter. Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers &. Fetching JSON, appending to array: Escaping closure captures mutating 'self' parameter Hot Network Questions Exploring the Concept of "No Mind" in Eastern Philosophy: An Inquiry into the Foundations and Implications Many thanks Error: Escaping closure captures mutating 'self' parameter import Combine import Foundation // Model protocol Fetchable { associatedtype T: Decodable var foo: [T] { get set } } extension Fetchable { internal mutating func fetch( from url: URL ) { let _: AnyCa. Non-escaping closure can't capture mutating self in Swift 3. I find a pitfall when using value type and escaping closure together. 函数执行闭包（或不执行）. Closure cannot implicitly capture a mutating self parameter, while using it on mutating Int method I'm trying to create an extension for Int, that increments its value progressively through time. When you declare a function that takes a closure as one of its parameters, you can write @escaping before the parameter’s type to indicate that the closure is allowed to escape. Which mean they cannot be mutated. Error: Escaping closure captures mutating 'self' parameter Whenever I need to capture a mutating instance of self, I must call a mutating function on the type itself after it has been initialized. completion (self. Easiest way is to use the capture list when creating escaping closure, and in that capture list you explicitly capture self as a weak reference:Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the companyerror: Converting non-escaping parameter 'completionHandler' to generic parameter 'Element' may allow it to escape By Definition: "A non escaping closure goes out of the scope and stops existing in memory as soon as the function body gets executed. g. but how to fix my code then? If f takes a non-escaping closure, all is well. e. createClosure closure To work around this you can. md","path":"proposals/0001-keywords-as-argument. e. non-escaping的生命周期：. md","path":"proposals/0001-keywords-as-argument. You can set initial values inside init, but then they aren't mutable later. func loadData(){ LoadXZYAPI() { [weak self] (data:Any?) in guard let strongSelf = self else { return } strongSelf. Properties in a struct like this (View) are immutable. A good example of an escaping closure is a completion handler. i. 1 Answer. In this case, it tries to capture completion, which is a non-escaping parameter. The short version. For instance, you can define a nested function (either using func or using a closure expression) and safely mutate an inout parameter. Protocol '. Connect and share knowledge within a single location that is structured and easy to search. Heap and stack should all be completely abstracted for the swift programmer. "Implicit use of 'self' in closure; use 'self. I have tried using Timer except now I get Escaping closure captures mutating 'self' parameter for the timer because of the line lights[I]. finneycanhelp. . md","path":"proposals/0001-keywords-as-argument. I'm not sure how to approach this problem. Asperi. Also, you won't need to unwrap it each time you use it (The "aesthetic" part) In most cases, this makes sense, since once you start doing work in your closure, you likely want to do all that work. concurrent)//This creates a concurrent Queue var test = 10 mutating func example () { connectQueue. Do I need to use a class in this case? Or is there some implementation that I don't know/haven't thought of (maybe with Combine?)? Any advice is much appreciated! P. Contentview. Before we had `@noescape`, we still wanted `inout. I have boiled down my code to include only the pieces necessary to reproduce the bug. Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the companyA closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. 539. Fetch data from server swiftUI. Class _PointQueue is implemented in both. mfdeveloper / /Protocol '. This question already has answers here : Swift 5 : What's 'Escaping closure captures mutating 'self' parameter' and how to fix it (3 answers) Closed last year. com's AI search assistant which allows users to find summarized answers to questions without needing to browse multiple websites. According to the Swift language book, a closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. Non-Escaping Closures. Even in an -O build, although the heap allocation for the Bar instance is able to be optimised to a stack allocation for just the foo property, this still results in an unnecessary second reference to the Foo. Tuple, Any, Closure are non-nominal types. Escaping closure captures mutating 'self' parameter. My playground sample code looks like this: class MyFoo: ObservableObject { @Published var bar: String init (bar: String) { self. ios; swift; swiftui; Share. When you use an escaping closure from within a struct, you can only use an immutable capture of an instance. the closure that is capturing x is escaping kind or nonescaping kind. . Try below and let me know if it works: public struct ExampleStruct { let connectQueue = DispatchQueue (label: "connectQueue", attributes: . Escaping and Non-Escaping in Swift 3. Stack Overflow | The World’s Largest Online Community for DevelopersIs it possible to write a property wrapper that can fetch data from some API and update a SwiftUI view upon receiving the data in a similar way to how @FetchRequest fetches data from Core Data and updates the view with whatever it finds?. someProperty = somethingElse you aren't modifying the array and as long as the array contains reference objects (class instances) even if you did modify. id == instance. Closures can capture values from their environment in three ways, which directly map to the three ways a function can take a parameter: borrowing immutably, borrowing mutably, and taking ownership. Hi guys, im trying to get data from JSON and assign it to my struct's property, now it keeps saying that "self is immutable cause as far as i know struct is a value type, now I'm wondering what is a good way to assign my struct via JSON cause it doest let me to assign the info into the struct. In Swift 1. ~~A better way (IMO) would be to create a mutating func to do your firebase call and update the values inside mutating function. Value types are copied (at least effectively) on assignment, so if a closure captures a mutable value type which copy is being mutated? Early Swift had a compromise semantics which did the expected thing most of the time, but produced confusing results at. 0. Look at the below code:Mutating regular member var get error: "Cannot assign to property: 'self' is immutable" "Cannot use mutating member on immutable value: 'self' is immutable" struct porque: View { @State private var flag = false private var anotherFlag = false mutating func changeMe(_ value: Bool) { self. option 1 & 2 produce a compile error: "Escaping closure captures mutating 'self' parameter", this is an architectural issue, do not mutate a view state during view render cycle, rather change the view's data model outside of the render cycle and let the re-render of the view reflect that change, that is why - options 3 & 4 are preferred either. – Berik. Provide details and share your research! But avoid. When you declare a function that takes a closure as one of its parameters, you can write @escaping before the parameter’s type to indicate that the closure is allowed to escape. if self. { // assign function directly instead of via capturing closure viewModel = TimerViewModel(totalTime: 15, finished: timerCallback) } var body: some View { Text("Demo") } private func timerCallback. create () and @escaping notification closure work on different threads. Closure cannot implicitly capture self parameter. Firebase is asynchronous and values are only valid following the Firebase function, within the closure. Based on this and the empty set your descriptiveDate and descriptiveInt don't need to be Binding just a get for a String In Swift 1. Then in your is_new getter, compare the expiry time with the current time. Inside, there is another type Inner, which stores a closure that should, at some point, toggle the. {"payload":{"allShortcutsEnabled":false,"fileTree":{"proposals":{"items":[{"name":"0001-keywords-as-argument-labels. Learn when escaping is really useful. Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the company{"payload":{"allShortcutsEnabled":false,"fileTree":{"proposals":{"items":[{"name":"0001-keywords-as-argument-labels. 1. transform = CGAffineTransform(scaleX: 0. Compiler gives "closure cannot implicitly capture a mutating self parameter". ShareSwiftUI Escaping closure captures mutating 'self' parameter. I'm trying to create an extension for Int, that increments its value progressively through time. Swift ui Escaping closure captures mutating 'self' parameter. struct MyView: View { @State var current: Int = 0 var body: some View { Text (" (current)") . – ctietze. md","path":"proposals/0001-keywords-as-argument. lazy implies that the code only runs once. I have been working on a count down timer and it was going ok, but when i decided to restructure the code in MVC and moved part of the code i got this error. Xcode return: Escaping closure captures mutating 'self' parameter. and that's fine. SwiftUI Escaping closure captures mutating 'self' parameter. I tried to write an "editor" class that could retain a reference to a property on a different object for later mutation. Escaping closure captures mutating 'self' parameter. sorted (by: { $0. onResponse != nil { self. I have created a very simplified example to explain it: The View: import SwiftUI struct ContentView: View { @ ObservedObject var viewModel: ViewModel var body: some. Add a. init (responseDate)) { moveBack () } } private mutating func. swift class GetLocations :ObservableObject { @Published var arrLocations = NSArray () func getLocNames (Action:String, Id: String, completion: @escaping (NSArray) -> Void) { //fetch data from server let session = URLSession. Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand ; Advertising Reach developers & technologists worldwide; About the companyunderstood, problem is if I remove it I get warning Escaping closure captures mutating 'self' parameter – Damiano Miazzi. I use this boolean to show a view on a certain state of the view. 2. Closure captures 'escapingClosure' before it is declared. An @autoclosure attribute can be applied to a closure parameter for a function, and. And the result of the closure is indirectly used by transform, so it doesn't actually escape. 5 seco. increase() // may work } If you change model to reference type, i. 1 Answer. The first is to capture a reference to the struct, but in many cases it lives on the stack. dismiss () } } This isn't what I want. posts. scheduledTimer (withTimeInterval: 1. {"payload":{"allShortcutsEnabled":false,"fileTree":{"proposals":{"items":[{"name":"0001-keywords-as-argument-labels. MyView { MyContent() } but what I want is to pass a parameter in the closure, like. Swift ui Escaping closure captures mutating 'self' parameter. In the Core Audio Recorder example the AudioQueueInputCallback function is written as a variable binding outside the class Recorder. I know there are a lot of questions out there that have been answered on how to use @escaping functions in general. 6. md","path":"proposals/0001-keywords-as-argument. append(str) modifies the parent ContentView object out of dataTask closure and that is not good for some reason. The problem with capturing mutating self in an @escaping closure in a struct is there are really only two choices in how Swift might theoretically attempt to do it. Variable assignment with mutating functionality. Escaping closure captures mutating 'self' parameter Hello, I am new to swift programming and I've been having this error "Escaping closure captures mutating. To have a clean architecture app, you can do something like this. The whole point is the closure captures and can modify state outside itself. If you want to change local variables with callback you have to use class. Basically, it's about memory management (explicit/escaping vs. Escaping closure captures mutating 'self' parameter. [self] in is implicit, for. main. Cannot use mutating member on immutable value: 'self' is immutable. The first is to capture a reference to the struct, but in many cases it lives on the stack. The type owning your call to FirebaseRef. How do I reference a mutable variable in a completion handler (so that I can access it's property's value at the time that the completion handler is eventually called, not when it is captured) while avoiding the "Escaping closure captures mutating 'self' parameter" error?I have a boolean called 'isMatched'. This results in a strong reference cycle. You can use a backtick to escape reserved words: struct Links: Codable { var `self`: String } If you don't want to use self, you can map a json key to a different property using manually defined CodingKeys: struct Links: Codable { var me: String enum CodingKeys: String, CodingKey { case me = "self" } }test. numberToDisplay += 1 // you can't mutate a struct without mutating function self. // Closure cannot implicitly capture a mutating self parameter. in the closure, but when using [unowned self], you can omit self. SwiftUI pass func as parameter where func has a generic parameter. Click again to stop watching or visit your profile to manage watched threads and notifications. If you said someArray[index] = something you are modifying the array. 0 Swift for loop is creating new objects. observeSingleEvent(of:with:) is most likely a value type (a struct?), in which case a mutating context may not explicitly capture self in an @escaping closure. This dissertation is an ethnographic study, accomplished through semi-structured interviews and participant observation, of the cultural world of third party Apple software developers who use Apple’s Cocoa libraries to create apps. It does not create any breaking change, as long the default rule for optional parameter closures keeps them @escaping. If we are sending some self value into it, that will risk the closure behave differently upon its execution. A copy is used to ensure that the closure can use self without having to use self, as the compiler will complain that "Escaping closure captures mutating self parameter" (hence the reason that OverlapContainer has two. 将闭包传递给函数. Escaping closure captures mutating 'self' parameter. Escaping closure captures mutating 'self' parameter (I really need help!) Dec '21. 0, repeats: true) { _ in count += 1} } } But moving timer creation to a function eliminates the error:Escaping closure captures mutating ‘self’ parameter. parameter, result: result) } } As you've probably noticed, this will cause a memory leak, since onSuccess is an escaping closure and it's retaining self. Escaping closure captures mutating 'self' parameter !! presentationMode. import Combine class GameViewModel: ObservableObject { @Published var game : Game @Published var user : User? init (game: Game) { self. 如果考虑到内存的. anotherFunction(parameter: self.