在Objective-C中复制块（即：将它们复制到实例变量） [英] Copying blocks (ie: copying them to instance variables) in Objective-C

问题描述

我试图理解块。我得到如何正常使用它们，当直接传递给一个方法。我现在感兴趣的是取一个块，将它（说）存储在一个实例变量中并稍后调用它。

块编程指南使它听起来像我可以做这通过使用Block_copy / retain来复制块，但是当我尝试运行它我崩溃我的程序。

  （void）setStoredBlock 
 {
 int salt = 42; 
 m_storedBlock = ^（int incoming）{return 2 + incoming + salt; }; 
 [m_storedBlock retain]; 
} 
  

我尝试稍后调用它：

   - （void）runStoredBlock 
 {
 int outputValue = m_storedBlock（5）; 
 NSLog（@当我们运行我们存储的blockwe回来：％d，outputValue）; 
 [m_storedBlock release]; 
} 
  

任何人都有什么见解？

非常感谢！

$ b {
int salt = 42;
m_storedBlock = Block_copy（^（int incoming）{return 2 + incoming + salt;}）;
}

I'm trying to understand blocks. I get how to use them normally, when passed directly to a method. I'm interested now in taking a block, storing it (say) in an instance variable and calling it later.

The blocks programming guide makes it sound like I can do this, by using Block_copy / retain to copy the block away, but when I try to run it I crash my program.

- (void) setupStoredBlock
{
    int salt = 42;
    m_storedBlock = ^(int incoming){ return 2 + incoming + salt; };
    [m_storedBlock retain];
}

I try to call it later:

- (void) runStoredBlock
{
    int outputValue = m_storedBlock(5);
    NSLog(@"When we ran our stored blockwe got back: %d", outputValue);
    [m_storedBlock release];
}

Anyone have any insights? (Or, is there something I'm not getting with blocks?)

Thank you very much!

解决方案

You'll want to do this instead:

- (void) setupStoredBlock
{
    int salt = 42;
    m_storedBlock = Block_copy(^(int incoming){ return 2 + incoming + salt; });
}

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