Swift中的use块给出了错误“变量在其自身初始值内使用”。 [英] Use block in Swift giving error "Variable used within its own initial value"

问题描述

这是我在obj-c中的代码：

This is my code in obj-c:

__block NSString *requestReference = [self operation:method url:url parameters:parameters headers:headers success:^(NSURLSessionDataTask *task, id responseObject) {
NSError *error = [NSError errorWithSessionTask:task responseObject:responseObject];
if (error) {
    NSLog(@"error - %@", error);
    [delegate requestWithReference:requestReference didFinishWithBusinessError:error];
} else {
    id responseModel;
    if (modelClass && responseObject) {
        if ([responseObject isKindOfClass:[NSDictionary class]]) {
            // if response is a dictionary, create model out of it
            responseModel = [modelClass objectFromDictionary:responseObject error:&error];
        } else if ([responseObject isKindOfClass:[NSArray class]]) {
        }
    }
} } failure:^(NSURLSessionDataTask *task, NSError *error) {
[delegate requestWithReference:requestReference didFailWithError:error]; }];

这是在Swift中转换后的代码：

and this is the code after conversion in Swift:

var requestReference = self.operation(method, url: url, parameters: parameters, headers: headers, success: {(_ task: URLSessionDataTask, _ responseObject: Any) -> Void in
    var error = Error(sessionTask: task, responseObject: responseObject)
    if error {
        print("error - \(error)")
        delegate.request(with: requestReference, didFinishWithBusinessError: error)
    }
    else {
        var responseModel: Any!
        if modelClass && responseObject {
            if (responseObject is [AnyHashable: Any]) {
                // if response is a dictionary, create model out of it
                do {
                    responseModel = try modelClass.object(fromDictionary: responseObject)
                }
                catch {
                }
            }
            else if (responseObject is [Any]) {

            }
        }
    }
}, failure: {(_ task: URLSessionDataTask, _ error: Error) -> Void in
    delegate.request(with: requestReference, didFailWithError: error)
})

我已经转换并提出了这段代码。
一切都在此代码中运行
但我遇到了错误：

I have converted and come up with this code. everything is working in this code But I'm getting error:

变量在其自身的首字母内使用value

"Variable used within its own initial value"

推荐答案

Swift编译器非常严格，并检查每个变量是否具有$ b $在使用之前定义的值。编译器
不知道在您的情况下，闭包将仅在定义 requestReference 变量之后的
之后执行。 。

The Swift compiler is very strict and checks that every variable has a defined value before it is used. The compiler does not know that in your case, the closures will be executed only after the requestReference variable is defined.

在这种情况下，您可以使用隐式解包可选：

In such cases you can use an implicitly unwrapped optional:

var requestReference: String! 
requestReference = self.operation(..., success: {(_ task: URLSessionDataTask, _ responseObject: Any) -> Void in
    // ... 
    delegate.request(with: requestReference, didFinishWithBusinessError: error)
}, failure: {(_ task: URLSessionDataTask, _ error: Error) -> Void in
    delegate.request(with: requestReference, didFailWithError: error)
})

一个隐式展开的可选内容是对编译器的承诺：
变量没有值现在，但使用时将具有值。

An implicitly unwrapped optional is a promise to the compiler: The variable has no value now, but it will have a value when it is used.

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