iOS属性字符串NSMutableAttributedString

btnAgreement.contentEdgeInsets = UIEdgeInsetsMake(0, 0, 0, -5);
btnAgreement.titleLabel.font = [UIFont systemFontOfSize:14];
NSString *agreementStr = @"我已阅读并同意许可服务协议";
NSMutableAttributedString *agreementAtrStr = [[NSMutableAttributedString alloc]initWithString:agreementStr];
[agreementAtrStr addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:[agreementStr rangeOfString:@"许可服务协议" ]];//“许可服务协议”这几个字是蓝色的
[btnAgreement setAttributedTitle:agreementAtrStr forState:UIControlStateNormal];