#pragma mark - 初始化构造字符串
NSString *str = [[NSString alloc]initWithString:@"Hell kitty"];
NSString *str2 = [[NSString alloc]initWithFormat:@"zzzz%d", 110];
NSLog(@"%@", str);
NSLog(@"%@", str2);
#pragma mark - 便利构造器的初始化方法
NSString *str3 = [NSString stringWithString:@"jjjjj"];
NSString *str4 = [NSString stringWithFormat:@"我是%@", @"张杰"];
NSLog(@"%@", str3);
NSLog(@"%@", str4);
#pragma mark - 常用操作
//获取字符串长度
NSString *str5 = @"zhang jiemiaoshuang";
NSLog(@"%lu", [str5 length]);
//判断字符串是否以制定字符串开始或者结束
NSLog(@"%d", [str5 hasPrefix:@"zhang2"]);
NSLog(@"%d", [str5 hasSuffix:@"ang"]);
//判断某个字符串是否在里面（字符串截取）
NSLog(@"%@", [str5 substringFromIndex:5]);
NSLog(@"%@", [str5 substringToIndex:5]);//
NSLog(@"%@", [str5 substringWithRange:NSMakeRange(2, 5)]);//从哪里开始 截取多少位
//字符串拼接
NSLog(@"%@", [str5 stringByAppendingString:@"哈哈哈"]);
NSLog(@"%@", [str5 stringByAppendingFormat:@"%@",@"哈哈哈"]);
//字符串比较
NSString *str6_1 = @"zhangjie";
NSString *str6_2 = @"miaoshuang";
NSComparisonResult res = [str6_1 compare:str6_2];
if ( res== NSOrderedAscending) {
NSLog(@"后面大");
}else if(res == NSOrderedSame){
NSLog(@"相等");
}else{
NSLog(@"前面大");
}
//字符串替换
str5 = [str5 stringByReplacingOccurrencesOfString:@"miaoshuang" withString:@"苗爽"];
NSLog(@"%@", str5);
//大小写转换
str5 = [str5 uppercaseString];
NSLog(@"%@", str5);
str5 = [str5 lowercaseString];
NSLog(@"%@", str5);
str5 = [str5 capitalizedString];
NSLog(@"%@", str5);
//字符串和数值类型的装换
//数值类型-->字符串
NSString *str7 = [NSString stringWithFormat:@"%d", 4];
//字符串-->数值
NSInteger i = [str7 integerValue];
NSLog(@"%ld", i);
#pragma mark - NSMutableString（可变字符串）
NSMutableString *mutableStr = [NSMutableString stringWithString:@"zhangjie"];
//拼接字符串
[mutableStr appendString:@"love miaoshuang"];
NSLog(@"%@", mutableStr);
//插入字符串
[mutableStr insertString:@"hahah" atIndex:10];
NSLog(@"%@", mutableStr);
//删除字符串
[mutableStr deleteCharactersInRange:NSMakeRange(2, 10)];
NSLog(@"%@", mutableStr);
原文：http://my.oschina.net/zhangjie9142/blog/500148