NSAttributedString字符串属性类

//定义一个可变字符串属性对象aStr
NSMutableAttributedString *aStr = [[NSMutableAttributedString alloc]initWithString:str];
//定义一个字典类对象dic存储设置的属性值，这里设置字体为粗体     
NSDictionary *dic = @{NSFontAttributeName:[UIFont boldSystemFontOfSize:self.myLabel.font.pointSize]   ,NSBackgroundColorAttributeName:[UIColor redColor]};
//定义要改变的字符串的范围
    NSRange myRange = [str rangeOfString:title];
//调用aStr对象的setAttributes方法设置属性
    [aStr setAttributes:dic range:myRange];
//把aStr对象赋给Label
    self.myLabel.attributedText = aStr;