Objective-C 中核心处理字符串的类是 NSString 与 NSMutableString ,这两个类最大的区别就是NSString 创建赋值以后该字符串的内容与长度不能在动态的更改,除非重新给这个字符串赋值。而NSMutableString 创建赋值以后可以动态在该字符串上更改内容与长度。
1.创建NSString字符串
NSString 与 char* 最大的区别就是 NSString是一个objective对象,而char* 是一个字节数组。@+" 字符串 " 这个符号为objective-c NSString 字符串常量的标准用法,char* 创建的时候 无需添加@
- - (void)viewDidLoad
- {
- [super viewDidLoad];
- //经典的字符串赋值
- NSString *str0 = @"my name is justcoding !";
- //字符串格式化合并分别包括
- //NSString*类型 int类型 char*类型
- NSString *str1 = [NSString stringWithFormat:@"我的名字:%@ 我的年龄:%d 我的邮箱:%s",@"justcoding", 25,"justcoding@gmail.com"];
- //字符串赋值 参数中只可以写一个字符串 和第一种很像
- NSString *str2 = [NSString stringWithString:@"我是字符串"];
- //字符串转换为utf-8格式 参数为char*类型
- NSString *str3 = [NSString stringWithUTF8String:"字符串转换utf-8格式"];
- //字符串合并
- int i = 100;
- char*c = "xuanyusong";
- NSString *temp = @"我是临时字符串";
- //在字符串temp的基础继续添加 int i 与 char* c 组成一个新的字符串
- NSString *str4 = [temp stringByAppendingFormat:@"整型: %d 字符型 :%s",i,c];
- //在字符串temp的基础继续添加temp 并组成一个新的字符串
- NSString *str5 = [temp stringByAppendingString:temp];
- //字符串输出
- NSLog(@"str0 = %@", str0);
- NSLog(@"str1 = %@", str1);
- NSLog(@"str2 = %@", str2);
- NSLog(@"str3 = %@", str3);
- NSLog(@"str4 = %@", str4);
- NSLog(@"str5 = %@", str5);
- }
2.字符串的遍历
每一个字符串其实是由若干个char字符组成,字符串的遍历实际上就是将字符串中的每一个字符提取出来。
- - (void)viewDidLoad
- {
- [super viewDidLoad];
- //经典的字符串赋值
- NSString *str = @"YUSONGMOMO";
- //字符串的长度
- int count = [str length];
- NSLog(@"字符串的长度是%d",count);
- //遍历字符串中的每一个字符
- for(int i =0; i < count; i++)
- {
- char c = [str characterAtIndex:i];
- NSLog(@"字符串第 %d 位为 %c",i,c);
- }
- }
3.字符串的比较
isEqualToString 比较字符串是否完全相等,大小写不一样也无法完全匹配。
hasPrefixe 匹配字符串头
haSuffix 匹配字符串的尾巴
- - (void)viewDidLoad
- {
- [super viewDidLoad];
- NSString *str0 = @"justcoding";
- NSString *str1 = @"justcoding";
- //字符串完全相等比较
- if([str0 isEqualToString:str1])
- {
- NSLog(@"字符串完全相等");
- }
- //字符串以开头比较
- if([str0 hasPrefix:@"just"])
- {
- NSLog(@"字符串str0以just开头");
- }
- //字符串以结尾比较
- if([str1 hasSuffix:@"coding"])
- {
- NSLog(@"str1字符串以coding结尾");
- }
- }
- //isEqualToString方法
- NSString *astring01 = @"This is a String!";
- NSString *astring02 = @"This is a String!";
- BOOL result = [astring01 isEqualToString:astring02];
- NSLog(@"result:%d",result);
- //compare方法(comparer返回的三种值)
- NSString *astring01 = @"This is a String!";
- NSString *astring02 = @"This is a String!";
- BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
- NSLog(@"result:%d",result);
- //NSOrderedSame 判断两者内容是否相同
- NSString *astring01 = @"This is a String!";
- NSString *astring02 = @"this is a String!";
- BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
- NSLog(@"result:%d",result);
- //NSOrderedAscending 判断两对象值的大小(按字母顺序进行比较,astring02大于astring01为真)
- NSString *astring01 = @"this is a String!";
- NSString *astring02 = @"This is a String!";
- BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;
- NSLog(@"result:%d",result);
- //NSOrderedDescending 判断两对象值的大小(按字母顺序进行比较,astring02小于astring01为真)
- //不考虑大 小写比较字符串1
- NSString *astring01 = @"this is a String!";
- NSString *astring02 = @"This is a String!";
- BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
- NSLog(@"result:%d",result);
- //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较,astring02小于astring01为 真)
- //不考虑大小写比较字符串2
- NSString *astring01 = @"this is a String!";
- NSString *astring02 = @"This is a String!";
- BOOL result = [astring01 compare:astring02 options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame;
- NSLog(@"result:%d",result);
- //NSCaseInsensitiveSearch:不区分大小写比较 NSLiteralSearch:进行完全比较,区分大小写 NSNumericSearch:比较字符串的字符个数,而不是字符值。
判断的方法可以利用 NSString 类别中 caseInsensitiveCompare: 所回传 -1、0 或是 1 的数值,判定两个字串之间得排序关系,其程式玛如下。
- NSString *string = @"0";
- NSComparisonResult result = [string caseInsensitiveCompare:@"A"];
- switch (result) {
- case NSOrderedAscending:
- NSLog(@"升幂");
- break;
- case NSOrderedSame:
- NSLog(@"忽略大小写相同的字串");
- break;
- case NSOrderedDescending:
- NSLog(@"降幂");
- break;
- default:
- NSLog(@"无法判定");
- break;
- }
4. 文件字符串操作(读写)
- //从文件读取字符串:initWithContentsOfFile方法
- NSString *path = @"astring.text";
- NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
- NSLog(@"astring:%@",astring);
- [astring release]; //astring=nil;
- //写字符串到文件:writeToFile方法
- NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
- NSLog(@"astring:%@",astring);
- NSString *path = @