在iOS ARC中，我的递归函数使用EXC_BAD_ACCESS使应用程序崩溃

Question

Following code of mine generates crash in ARC mode:

MxTextField.m

+enableAllTextFields:(BOOL)enable InViews:(__weak UIView*) view
{

   @try
   {
      NSArray* textFields = view.subViews;

      for(int idx = 0; idx < textFields.count; idx++)
      {
         __weak UIView* view = [textFields objectAtIndex:idx];

         if(view.subViews.count > 0)
            [MxTextField enableAllTextFields:enable InView:view];
         else
            NSLog(@"No SubViews");

         if([view class] == [MxTextField class])
            [(MxTextField*) view setEnabled:enable];
      }

   }
   @catch(NSException exception)
   {
      NSLog(@"%s : %@",__func__,exception);
   }

}

After Some Loop on the execution of this function It crashes by showing breakpoint at the end of the function saying EXC_BAD_ACCESS. Can anyone help me out that what goes wrong in this implementation?

Any help will be thankful.

Answer 1

The problem could be the method adopted for iteration and also try-catch is not a good practice, use fast-enumeration for faster and reliable result . The below code could resolve your problem

+(void)enableAllTextField:(BOOL)enable inView:(UIView *)contrainerView
{
    for (UIView *subview in contrainerView.subviews) {
        if(subview.subviews.count>0)
             [MxTextField enableAllTextField:enable inView:subview];
        else if ([subview isKindOfClass:[MxTextField class]]) {
             MxTextField *textField = (MxTextField *)subview;
             [textField setEnabled:enable];
        }
    }
}

Answer 2

Putting aside many other problems the only reason for a crash that I can see from the posted code is that your method is supposed to return an object but does not do so.

Explanation: While it's not common to leave out the return type in Objective-C it's perfectly legal. It means that the method returns an object of type id.

Since your method lacks a return statement the returned value is undefined. This confuses ARC and probably makes it autorelease the random value in the return register which, eventually, leads to the crash.

Here's a proper version of your method:

+ (void)forAllTextFieldsIn:(UIView *)view setEnabled:(BOOL)enabled
{
    if ([view isKindOfClass:[MxTextField class]])
        [(MxTextField *)view setEnabled:enabled];

    for (UIView *subview in view.subviews)
        [self forAllTextFieldsIn:subview setEnabled:enabled];
}