2、NSString *log=@"北京欢迎您a"; //[NSString stringWithFormat:@"I am ‘%@‘",Beijing]; //字符串格式化

3、NSString *zhui = [Beijing stringByAppendingString:@"哈哈哈"]; //字符串追加

结果是北京欢迎您哈哈哈；append意思为附加挂上；

4、bool b=[Beijing isEqualToString:log]; //字符串比较

5、NSString *hh = @"http://www.sina.com.cn";
    if([hh hasPrefix:@"http"]){                                          //查找以http开头的字符串
        NSLog(@"含有http");
    }else{
        NSLog(@"没有http");
    }
6、 NSString *ss = @"123";
int a = [ss intValue]+13;                                   //字符串转int型
double dd = [ss doubleValue]+33.3;                          //字符串转double型
NSLog(@"%g",dd);
7、字符串转数组
    NSString *zifuchuan =@"one,two,three,four";
    NSLog(@"string:%@",zifuchuan);
    NSArray *array = [zifuchuan componentsSeparatedByString:@","];
//    NSLog(@"array:%@",array);                             //输出整个数组中所有元素

结果：

2015-08-19 16:30:19.900 Demo[93879:4702032] string:one,two,three,four

2015-08-19 16:30:19.901 Demo[93879:4702032] array:( one, two, three, four)

NSString *value = [array objectAtIndex:0]; //取出第0个元素
NSLog(@"value:%@",value);

结果：

2015-08-19 16:33:03.577 Demo[93917:4703555] value:one
8、//数组转字符串
NSString * zifuchuan2 = [array componentsJoinedByString:@","];
NSLog(@"zifuchuan2:%@",zifuchuan2);
结果：zifuchuan2:one,two,three,four
9、-substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringToIndex:3];
NSLog(@"string2:%@",string2);

结果：string2:Thi

10、-substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@"string2:%@",string2);

结果：2015-08-19 16:41:51.772 Demo[94021:4708352] string2:s is a string

11、-substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@"string2:%@",string2);
结果：string2:This

//去除字符串中用括号括住的位置
-(NSString *)handleStringWithString:(NSString *)str{

NSMutableString * muStr = [NSMutableString stringWithString:str];
while (1) {
NSRange range = [muStr rangeOfString:@"("];
NSRange range1 = [muStr rangeOfString:@")"];
if (range.location != NSNotFound) {
NSInteger loc = range.location;
NSInteger len = range1.location - range.location;
[muStr deleteCharactersInRange:NSMakeRange(loc, len + 1)];
}else{
break;
}
}

return muStr;
}

--------操作动态字符串--NSMutableString----------------------------------------------------
    NSMutableString *mstr = [[NSMutableString alloc] init];实例话一个可变字符串；
    NSString *str1 = @"This is a example.";
    //创建可变字符串
    mstr = [NSMutableString stringWithString:str1];
    //插入字符
    [mstr insertString:@"very easy " atIndex:10];

结果：

2015-08-19 16:48:13.620 Demo[94107:4712065] This is a very easy example.

[mstr deleteCharactersInRange:NSMakeRange(10,5)];//删除一些字符

结果：2015-08-19 16:51:54.396 Demo[94184:4714267] This is a easy example.

//查找并删除
    NSRange substr = [mstr rangeOfString:@"example"];             //字符串查找,可以判断字符串中是否有
    if (substr.location != NSNotFound) {
        [mstr deleteCharactersInRange:substr];
    }
    //重新设置字符串
    [mstr setString:@"This is string AAA"];
    //替换字符串
    [mstr replaceCharactersInRange:NSMakeRange(15, 2) withString:@"BBB"];   //从第15个字符串处替换掉后2个字符串
结果：2015-08-19 16:54:14.757 Demo[94216:4715472] This is string BBBA

//查找第一个并替换
    NSString *search = @"This is";
    NSString *replace = @"An example of";
    substr = [mstr rangeOfString:search];// substr类型为nsrange；
    if (substr.location != NSNotFound) {
        [mstr replaceCharactersInRange:substr withString:replace];      //把第1个遇到的substr替换为replace
        NSLog(@"%@",mstr);
    }

//rangeOfString 前面的参数是要被搜索的字符串，后面的是要搜索的字符

//NSNotFound 表示请求操作的某个内容或者item没有发现，或者不存在

//查找全部匹配的，并替换
    search = @"a";
    replace = @"X";
    substr = [mstr rangeOfString:search];
    while (substr.location != NSNotFound) {
        [mstr replaceCharactersInRange:substr withString:replace];
        substr = [mstr rangeOfString:search];
    }

NSLog(@"%@",mstr);

Objective-C之NSString和NSMutableString

2、NSString *log=@"北京欢迎您a"; //[NSString stringWithFormat:@"I am ‘%@‘",Beijing]; //字符串格式化