iOS textfield設置字符間距

添加富文本屬性：

NSDictionary *attrsDictionary =@{
                    NSFontAttributeName: self.textField.font,
                    NSKernAttributeName:[NSNumber numberWithFloat:10.0f]//這里修改字符間距
                    };
self.textField.attributedText=[[NSAttributedString alloc]initWithString:text attributes:attrsDictionary];