带有完成块的递归方法

Question

我调用我的方法：

[self getBoundariesForFields:fields index:0 withCompletionBlock:^{
    DLog(@"completionBlock fields: %@", fields);
}];

方法：

-(void)getBoundariesForFields:(NSArray *)fields index:(NSInteger)index withCompletionBlock:(void(^)())completionBlock {

if (index < fields.count) {
    NSMutableDictionary *field = [fields objectAtIndex:index];

    [self getBoundariesForField:field withCompletionBlock:^{
        [self getBoundariesForFields:fields index:index + 1 withCompletionBlock:^{
        }];
    }];
}
else {
    DLog(@"else statement fields: %@", fields);
    completionBlock();
}

}

我得到“else statement fields:”日志，但“completionBlock Fields:”从未运行。

我猜这与保留问题有关；调用此递归循环的原始方法被取消引用，因此当调用 completionBlock 时，代码消失了。

如何防止这种情况发生？

Answer 1

该块正在运行，但对该方法的递归调用传递的是一个空块^{}。通过传递原始块参数来修复...

-(void)getBoundariesForFields:(NSArray *)fields index:(NSInteger)index withCompletionBlock:(void(^)())completionBlock {

    if (index < fields.count) {
        NSMutableDictionary *field = [fields objectAtIndex:index];

        [self getBoundariesForField:field withCompletionBlock:^{
            // NOTICE change here...
            [self getBoundariesForFields:fields index:index + 1 withCompletionBlock:completionBlock];
        }];
    }  else {
        DLog(@"else statement fields: %@", fields);
        completionBlock();
    }
}