如何使用ARC将一个块实例化为实例变量? [英] How does one instantiate a block as an instance variable using ARC?

问题描述

要做什么才能使这种工作正常进行?

What does one do to make something like this work?

void (^)(void) *someBlock = ^{
  //some code
};

推荐答案

德米特里(Dmitry)的答案完全正确.将块语法视为C函数声明:

Dmitry's answer is exactly right. Think of the block syntax as a C function declaration:

// C function -> <return type> <function name> (<arguments>)
void someFunction(void) 
{
  // do something
}

// block -> <return type> (^<block variable name>) (<arguments>)
void (^someBlock)(void) = ^{
    // do something
};

另一个例子:

// C function
int sum (int a, int b)
{
    return a + b;
}

// block
int (^sum)(int, int) = ^(int a, int b) {
    return a + b;
};

因此，只需将块语法视为C函数声明即可: 首先是返回类型int，然后是块变量(^sum)的名称，然后是参数类型(int, int)的列表.

So just think of the block syntax as a C function declaration: First the return type int, then the name of the block variable (^sum) and then the list of arguments types (int, int).

但是，如果您经常在应用中需要某种类型的阻止，请使用typedef:

If, however, you need a certain type of block frequently in your app, use a typedef:

typedef int (^MySumBlock)(int, int);

现在您可以创建MySumBlock类型的变量:

Now you can create variables of the MySumBlock type:

MySumBlock debugSumBlock = ^(int a, int b) {
    NSLog(@"Adding %i and %i", a, b);
    return a + b;
};

MySumBlock normalSumBlock = ^(int a, int b) {
    return a + b;
};

希望有帮助:)

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