設置UItextfiled的placehold的顏色和大小

 _rightTF.placeholder = @"請輸入註冊時的手機號碼";
        NSMutableDictionary *dict = [NSMutableDictionary dictionary];
        dict[NSForegroundColorAttributeName] = [UIColor colorWithRed:25/255.0 green:158/255.0 blue:253/255.0 alpha:0.4];
        NSAttributedString *attr = [[NSAttributedString alloc] initWithString:_rightTF.placeholder attributes:dict];
        [_rightTF setAttributedPlaceholder: attr];
        
        [_rightTF setValue:[UIFont boldSystemFontOfSize:15 * HomePageDefineWidth] forKeyPath:@"_placeholderLabel.font"];