Init对象在 - （void）方法中

Question

我有两个视图控制器类，classA和classB是classA的子类。

在classA中，我编写了一个方法startAnimation，可以显示ActivityIndicator之类的视图;

我尝试通过调用-(void)startAnimation在classB中使用[self startAnimation]，但效果不佳，但更改为-(BOOL)startAnimation效果很好。我还没有明白。请为我解释一下：

-(BOOL)startAnimation{
     __block bool a = NO;
    _displayViewForActivityIndicator = [[ProcessingIndicationView alloc] initWithFrame:CGRectMake(-self.view.frame.size.width, -self.view.frame.size.height, self.view.frame.size.width, self.view.frame.size.height)];
    [self.view addSubview:_displayViewForActivityIndicator];
    LogDebug(@"Start the method");
    [UIView animateWithDuration:1.0f
                      delay:0.0f
                    options:UIViewAnimationOptionBeginFromCurrentState
                 animations:^{
                     //end position:
                     _displayViewForActivityIndicator.frame = self.view.frame;
                 }
    completion:^(BOOL finished) {
         if (finished) {
             LogDebug(@"Finish animation");
         }
         a = YES;
    }];
    return a;
}