Foundation框架—字符串（NSString）

一 NSString不可变字符串

1.字符串的创建

//创建字符串常量

NSString *string1 = @"hello";

string1 = @"hello word";

//alloc创建一个字符串

NSString *string2 = [[NSString alloc] initWithString:@"hello"];

NSString *string3 = [[NSString alloc] initWithFormat:@"hello %@",string1];

NSLog(@"string2:%@",string2);

NSLog(@"string3:%@",string3);

2.字符串的拼接

NSString *str1 = @"张三";

NSString *str2 = @"李四";

NSString *str3 = @"王五";

NSInteger a = 10;

NSString *string4 = [[NSString alloc] initWithFormat:@"%@,%@,%@,%ld",str1,str2,str3,a];

NSLog(@"string4:%@",string4);

3.类方法创建字符串

NSString *string5 = [NSString stringWithString:@"这是一个字符串"];

NSString *string6 = [NSString stringWithFormat:@"hello %@",string5];

NSLog(@"%@",string6);

4.字符串的比较

NSString *s1 = @"zhangsan";

NSString *s2 = @"zhangsan";

//－－－－－－－－－－－－－－比较指针－－－－－－－－－－－－－－

if (s1 == s2) {

NSLog(@"指针地址一样");

}

//－－－－－－－－－－－－－－比较内容－－－－－－－－－－－－－－

//isEqualToString  区分大小写的

if ([s1 isEqualToString:s2]) {

NSLog(@"字符串内容一样");

}

  5.使用isEqualToString

NSString *string7 = [[NSString alloc] initWithFormat:@"abc%@",@"def"];

NSString *string8 = [[NSString alloc] initWithFormat:@"abc%@",@"def"];

if ([string7 isEqualToString:string8]) {

NSLog(@"string7和string8的内容一样");

}

if (string7 == string8) {

NSLog(@"string7和string8的指针一样");

}

6.比较大小

NSString *string9 = @"changXiAngwEilai";

NSString *string10 = @"Changxiangweilai";

//compare  区分大小写的比较

NSComparisonResult result = [string9 compare:string10];

if (result == NSOrderedDescending) {

NSLog(@"这是降序");

}else {

NSLog(@"这是升序");

}

//caseInsensitiveCompare:不区分大小写的比较

result = [string9 caseInsensitiveCompare:string10];

if (result == NSOrderedSame) {

NSLog(@"不区分大小写相同");

}

  7.判断字符串的开头

NSString *string11 = @"changxiangweilai";

if ([string11 hasPrefix:@"chang"]) {

NSLog(@"string11是以chang开头");

}

8.判断字符串的结尾

if ([string11 hasSuffix:@"lai"]) {

NSLog(@"string11是以lai结尾");

}

9.字符串转换

NSString *string12 = @"heLlO WoRd";

//将字符串转换成小写lowercaseString

NSLog(@"小写:%@",string12.lowercaseString);

//将字符串转换成大写uppercaseString

NSLog(@"大写:%@",string12.uppercaseString);

//首字母改成大写，其他小写capitalizedString

NSLog(@"首字母大写：%@",string12.capitalizedString);

10.字符串和基本数据类型转换

NSString *string13 = @"12";

//string－> int

NSInteger intValue = [string13 integerValue];

NSLog(@"intValue:%ld",intValue);

NSString *string14 = @"3.4";

float floatValue = [string14 floatValue];

NSLog(@"floatValue:%f",floatValue);

NSString *string15 = @"12";

[string15 boolValue];

11.字符串的长度

NSString *string15 = @"abcdefg";

NSUInteger length = string15.length;

NSLog(@"length:%ld",length);

12.根据下标获取字符

unichar c = [string15 characterAtIndex:3];

NSLog(@"c:%c",c);

13.字符串的截取

NSString *string16 = @"www.baidu.com";

//1.截取到某一个指定的位置  substringToIndex  （不包含当前的下标）

//    截取出www

NSString *subStr1 = [string16 substringToIndex:3];

NSLog(@"subStr1:%@",subStr1);

//2.从指定位置截取  substringFromIndex  （包含当前下标）

//截取出com

NSString *subStr2 = [string16 substringFromIndex:10];

NSLog(@"subStr2:%@",subStr2);

//3.从某一个指定的截取指定长度

//baidu

NSRange rg = {4,5};

NSString *subStr3 = [string16 substringWithRange:rg];

NSLog(@"subStr3:%@",subStr3);

14.字符串的追加

NSString *string17 = @"Andriod";

//在Andriod后面追加 iOS

NSString *appendStr1 = [string17 stringByAppendingString:@" iOS"];

NSLog(@"appendStr1:%@",appendStr1);

NSString *appendStr2 = [string17 stringByAppendingFormat:@" %@%d",@"iOS",9];

NSLog(@"appendStr2:%@",appendStr2);

15.字符串的检索

NSString *string18 = @"12345678@qq.com";

//检索字符串中的qq.com

NSRange rg1 = [string18 rangeOfString:@"qqcom"];

//返回的结果：如果找到了，则返回字符串的信息；如果找不带，则location会返回一个NSNotFound

NSLog(@"location:%ld  length:%ld",rg1.location,rg1.length);

if (rg1.location == NSNotFound) {

NSLog(@"找不到");

}

二. NSMutableString（可变字符串）

1.可变字符串的创建

//NSMutableString *mutStr1 = @"abc";  //不能这么写是常量@“abc”

NSMutableString *mutStr1 = [[NSMutableString alloc]  initWithString:@"字符串"];

2.插入数据

[mutStr1 insertString:@"可变" atIndex:0];

3.追加

[mutStr1 appendString:@"对象哈哈"];

4.删除

//删除“哈哈”

NSRange rg2 = [mutStr1 rangeOfString:@"哈哈"];

[mutStr1 deleteCharactersInRange:rg2];

5.替换

//（1）检索需要替换的字符串

NSRange rg4 = [mutStr1 rangeOfString:@"字符串"];

//（2）替换

[mutStr1 replaceCharactersInRange:rg4 withString:@"数组"];

NSLog(@"mutStr1:%@",mutStr1);

6.按照某个字符将字符串截取成若干个字符串

NSString *str = @"this is string";

NSArray *arr = [str componentsSeparatedByString:@" "];

NSLog(@"arr = %@",arr);