将块内的变量分配给块外的变量 [英] Assign a variable inside a Block to a variable outside a Block

问题描述

我收到错误

变量不可指派（缺少__block类型说明符）

Variable is not assignable (missing __block type specifier)

aPerson = participant; 。我如何确保块可以访问 aPerson 变量和 aPerson 变量可以返回？

on the line aPerson = participant;. How can I make sure the block can access the aPerson variable and the aPerson variable can be returned?

Person *aPerson = nil;

[participants enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {   
    Person *participant = (Person*)obj;

    if ([participant.gender isEqualToString:@"M"]) {
        aPerson = participant;
        *stop = YES;
    }
}];

return aPerson;

推荐答案

您需要使用这一行代码来解决问题：

You need to use this line of code to resolve your problem:

__block Person *aPerson = nil;

有关详细信息，请参阅本教程：块和变量

For more details, please refer to this tutorial : Blocks and Variables

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