从NSBlockOperation获取价值？

Question

大家好，我非常沮丧，因为我想改进代码，但没有得到好的结果这是我的一段代码

NSBlockOperation *blockOperation1 = [NSBlockOperation blockOperationWithBlock: ^{
        value1 = [self getDiferences:0.0 finx:width iniy:0.0 finy:cuartoheith image:imagen1 imagetoComapare:imagen2];
    }];
    [queue addOperation:blockOperation1];

NSBlockOperation *blockOperation2 = [NSBlockOperation blockOperationWithBlock: ^{
        value2 = [self getDiferences:0.0 finx:width iniy:0.0 finy:cuartoheith image:imagen1 imagetoComapare:imagen2];
    }];
    [queue addOperation:blockOperation2];

NSBlockOperation *blockOperation3 = [NSBlockOperation blockOperationWithBlock: ^{
        value3 = [self getDiferences:0.0 finx:width iniy:0.0 finy:cuartoheith image:imagen1 imagetoComapare:imagen2];
    }];
    [queue addOperation:blockOperation3];

NSBlockOperation *blockOperation4 = [NSBlockOperation blockOperationWithBlock: ^{
        value4 = [self getDiferences:0.0 finx:width iniy:0.0 finy:cuartoheith image:imagen1 imagetoComapare:imagen2];
    }];
    [queue addOperation:blockOperation4]; 

我想在NSBlockOperation之外使用此值，就像这样的valuetotal=value1+value2+value3+value4；请帮助或提供更好的解决方案

Answer 1

添加另一个依赖于其他操作的操作(使用addDependency:)，并在其中添加代码。对此操作进行排队。它将等待所有其他程序完成，然后使用它们的输出。

例如,

NSBlockOperation *blockOperationFinal = [NSBlockOperation blockOperationWithBlock: ^{
    valueTotal = value1 + value2 + value3 + value4;
}];

[blockOperationFinal addDependency:blockOperation1];
[blockOperationFinal addDependency:blockOperation2];
[blockOperationFinal addDependency:blockOperation3];
[blockOperationFinal addDependency:blockOperation4];

[queue addOperation:blockOperationFinal]; 

Answer 2

一个块操作就足够了，因为它可以添加更多的块，并并发执行，同时提供一个块在所有块完成时触发，如下所示：

NSMutableArray *array = [[NSMutableArray alloc] init];
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
    [array addObject:@"op1"];
}];
[operation addExecutionBlock:^{
    [array addObject:@"op2"];
}];

[[[NSOperationQueue alloc] init] addOperation:operation];
[operation setCompletionBlock:^{
    NSLog(@"array:%@", array);
}];