在目标C语法中使用* [英] Use of * in Objective C Syntax

问题描述

我在用一些客观的c语法苦苦挣扎.有人可以在下面的实例方法中详细说明*的用法.

I'm struggling a bit with some objective c syntax. Can someone please elaborate on the usage of * in the following instance method.

- (IBAction)sliderChanged:(id)sender{
    UISlider *slider = (UISlider *)sender;
}

我意识到我们正在创建一个类型为UISlider的变量，然后在将其转换为UISlider后将其设置为sender.但是，我不知道*的含义和原因

I realize that we are creating a variable typed as UISlider and then setting it to sender once it is cast as a UISlider. However, I don't understand what the * are for and why

UISlider slider = (UISlider)sender; 

不起作用.

推荐答案

*，像在C中一样，在类型中使用时表示指针(例如您的情况)并取消引用指针.

*, like in C, when used in a type denotes a pointer (such as your case) and to dereference a pointer.

指针只是一个变量，它包含其他内容(在您的示例中为UISlider对象)在内存中的地址.

A pointer is just a variable that contains the address in memory of something else, in your example a UISlider object.

在您的示例中，

UISlider *slider = (UISlider *)sender;

slider类型为UISlider *，或者是指向UISlider对象的指针.

slider is of type UISlider *, or a pointer to a UISlider object.

以下有关C语言中指针的教程也适用于Objective-C: 您需要了解的有关C语言中的指针的所有信息

The following tutorial about pointers in C also applies to Objective-C: Everything you need to know about pointers in C

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