无法分配价值:“自我"是不可变的 [英] Cannot assign to value: 'self' is immutable

问题描述

我正在尝试从NSMutableURLRequest的子类中的自定义init返回一个实例:

I am trying to return an instance from custom init in subclass of NSMutableURLRequest :

class Request: NSMutableURLRequest {

     func initWith(endPoint:String, methodType:RequestType, body:RequestBody,headers: [String:String]?) {
        self = NSMutableURLRequest.init(url: URL.init(string: endPoint, relativeTo: URL?))
       //return request

    }
}

但是编译器不允许这样做，并且出现错误无法分配给值:'self'是不可变的".解决此问题的正确方法是什么，为什么编译器会在此处返回错误.

But compiler does not allow to do the same and i get the error "Cannot assign to value: 'self' is immutable". What is the correct way to go about this and why does the compiler return an error here.

推荐答案

这是因为您的函数只是函数，而不是初始化程序.

This is because your function is merely a function, not an initializer.

请考虑以下示例:

class Request: NSMutableURLRequest {

    convenience init (endPoint:String, methodType:RequestType, body:RequestBody,headers: [String:String]?) {
        self.init(url: URL(string: endPoint)!)
    }

}

在这里，我们声明便捷初始化器，该初始化器通过调用指定的初始化器来返回一个新对象.您无需分配任何内容，因为init是在对象的构造(创建)时调用的.

Here we declare convenience initializer which returns a new object by calling designated initializer. You don't have to assign anything because the init is called upon construction (creation) of the object.

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