iOS7下 UISearchBar設定ReturnKeyType

- (void)setReturnKeyType{
    //ios7 不用這個有問題
    for (UIView *searchBarSubview in [self.searchBarWords subviews]) {
        for (UIView *subView in [searchBarSubview subviews]) {
            if ([subView conformsToProtocol:@protocol(UITextInputTraits)]) {
                @try {
                    [(UITextField *)subView setReturnKeyType:UIReturnKeyDone];
                    //[(UITextField *)searchBarSubview setKeyboardAppearance:UIKeyboardAppearanceAlert];
                }
                @catch (NSException * e) {
                    // ignore exception
                }
            }
        }
    }
}