Why does not work changing UIButton text via dot syntax?

问题

Is it possible to change UIButton title label text via dot syntax? The text is not changing if I do it via dot syntax:

self.myButton.titleLabel.text = [NSString stringWithString:@"Nop"];

But this one does:

[self.myButton setTitle: @"Yep" forState: UIControlStateNormal];

Text change works for pure UILabels, is UIButton a special case or something?

回答1:

This is because the text can be changed for a UIButton for several different states (Normal, Highlighted, etc). Apple simply chose to require explicit code to set the text. You could probably create a category to implement this, if you really wanted.

回答2:

UIButton's can reconfigure their titles for any of the UIControlState's (see here: UIControlState).

Since using the dot syntax doesn't set the title for any specific state, the UIButton is likely re-configuring the title for UIControlStateNormal, which is set to nothing.

回答3:

Try

myButton.titleLabel.text=@"foo";

here works

[]'s

来源：https://stackoverflow.com/questions/7000796/why-does-not-work-changing-uibutton-text-via-dot-syntax