字符串的创建
代码语言：javascript复制 NSString *str1 = @"ss";//存储在常量区
NSString *str2 = [NSString stringWithFormat:@"%@",@"ss"];//存储在堆区
NSString *str3 = [[NSString alloc]initWithFormat:@"%@",@"ss"];//存储在堆区
NSString *str4 = [NSString stringWithString:@"ss"];//其内部执行的时浅拷贝
NSLog(@"str1 = %p",str1);
NSLog(@"str2 = %p",str2);
NSLog(@"str3 = %p",str3);
NSLog(@"str4 = %p",str4);
地址打印.png
字符串读写
代码语言：javascript复制 NSString *str = @"abc";
NSError *error = nil;
BOOL flag = [str writeToFile:@"/Users/soso/Desktop/demo1/NSString/demo.txt" atomically:YES encoding:NSUTF8StringEncoding error:&error];
NSLog(@"%d",flag);
NSString *str1 = [NSString stringWithContentsOfFile:@"/Users/soso/Desktop/demo1/NSString/demo.txt" encoding:NSUTF8StringEncoding error:&error];
NSLog(@"%@",str1);//abc字符串的比较
代码语言：javascript复制 NSString *str1 = @"ABC";
NSString *str2 = @"abc";
//比较内容
NSLog(@"%d",[str1 isEqualToString:str2]);
//比较地址
NSLog(@"%d",str1 == str2);
//比较大小，其实是比较的ascii值
switch ([str1 compare:str2]) {
case NSOrderedAscending:
NSLog(@"升序");
break;
case NSOrderedSame:
NSLog(@"相同");
break;
case NSOrderedDescending:
NSLog(@"降序");
break;
default:
break;
}
//忽略大小写比较
switch ([str1 caseInsensitiveCompare:str2]) {
case NSOrderedAscending:
NSLog(@"升序");
break;
case NSOrderedSame:
NSLog(@"相同");
break;
case NSOrderedDescending:
NSLog(@"降序");
break;
default:
break;
}字符串的搜索
代码语言：javascript复制 NSString *str = @"https:image.baidu.com.image";
//判断以什么开头
if ([str hasPrefix:@"https:"]) {
NSLog(@"是URL");
}
//判断以什么结尾
if ([str hasSuffix:@"image"]) {
NSLog(@"是image");
}
//判断是否包含该字符串
NSRange range = [str rangeOfString:@"baidu"];
NSLog(@"位置：%lu--长度：%lu",(unsigned long)range.location,(unsigned long)range.length);//位置：12--长度：5
NSRange range1 = [str rangeOfString:@"baidus"];//没有找到
if (range1.location == NSNotFound) {
NSLog(@"没有找到");
}字符串截取
代码语言：javascript复制 NSString *str = @"abcdefgabcd";
NSString *str1 = [str substringWithRange:NSMakeRange(1, 4)];
NSLog(@"%@",str1);//bcde
NSLog(@"%@",str);//abcdefgabcd
//截取的起始位置(默认从左往右找，找到就停了)
NSRange range2 = [str rangeOfString:@"a"];
NSLog(@"%zd,%zd",range2.location,range2.length);//0,1
//截取的起始位置(可以设置查找方向，找到就停了)
NSRange range22 = [str rangeOfString:@"a" options:NSBackwardsSearch];
NSLog(@"%zd,%zd",range22.location,range22.length);//7,1
//从什么地方开始截取，一直到最后
NSString *str3 = [str substringFromIndex:5];
NSLog(@"%@",str3);//fgabcd
NSLog(@"%@",str);//abcdefgabcd
//从开始截取，一直截取到什么位置
NSString *str4 = [str substringToIndex:5];
NSLog(@"%@",str4);//fgabcd
NSLog(@"%@",str);//abcdefgabcd字符串替换
代码语言：javascript复制 //替换内容
NSString *str = @"sayhi!";
NSString *str2 = [str stringByReplacingOccurrencesOfString:@"hi" withString:@"hello"];
NSLog(@"%@",str2);//sayhello
//移除两端字符串
NSString *str4 = @"AAsayAAhi!AA";
//两端移除字符串集合
NSString *str3 = [str4 stringByTrimmingCharactersInSet:[NSCharacterSet uppercaseLetterCharacterSet]];
NSLog(@"%@",str3);字符串与路径
代码语言：javascript复制 NSString *pathStr = @"/user/app/Desktop/info.txt";
//判断是否是绝对路径（本质就是判断字符串是否以/开头）
if ([pathStr isAbsolutePath]) {
NSLog(@"绝对路径");
}
//获取文件路径中的最后一个目录（本质就是获取路径中最后一个目录）
NSString *lastStr = [pathStr lastPathComponent];
NSLog(@"%@",lastStr); //info.txt
//删除路径中的最后一个目录（本质就是删除最后一个斜线的目录，包括斜线）
NSString *deletStr = [pathStr stringByDeletingLastPathComponent];
NSLog(@"%@",deletStr);///user/app/Desktop
//给路径添加一个目录（本质就是在字符串末尾加上一个斜线和指定内容）
NSString *addStr = [pathStr stringByAppendingPathComponent:@"/abc"];
NSLog(@"%@",addStr);///user/app/Desktop/info.txt/abc
//获取路径中文件的扩展名
NSString *extensionStr = [pathStr pathExtension];
NSLog(@"%@",extensionStr);//txt
//删除路径中文件的扩展名(本质就是从字符串的末尾查找，截取第一个后面的内容)
NSString *deletExtensionStr = [pathStr stringByDeletingPathExtension];
NSLog(@"%@",deletExtensionStr);///user/app/Desktop/info
//给文件路径中添加一个扩展名（本质就是在字符串的末尾加上一个点和指定的内容）
NSString *addExtensionStr = [pathStr stringByAppendingPathExtension:@"jpg"];
NSLog(@"%@",addExtensionStr);///user/app/Desktop/info.txt.jpg字符串转换
代码语言：javascript复制 NSString *str = @"aBcD";
//转大写
NSLog(@"%@",[str uppercaseString]);//ABCD
//转小写
NSLog(@"%@",[str lowercaseString]);//abcd
//转数字
NSString *str1 = @"234";
int value = [str1 intValue];
NSLog(@"%d",value);//234
NSString *str3 = @"abc";
const char *c = [str3 UTF8String];
NSLog(@"%s",c);//abc
const char *c1 = "abc";
NSString *str4 = [NSString stringWithUTF8String:c1];
NSLog(@"%@",str4);//abcNSMutableString
代码语言：javascript复制 NSMutableString *str = [NSMutableString string];
NSLog(@"%@",str);
//字符串拼接
[str appendString:@"abcdefg"];
//删除
[str deleteCharactersInRange:NSMakeRange(2, 2)];
NSLog(@"%@",str);//abefg
//插入
[str insertString:@"PPP" atIndex:4];
NSLog(@"%@",str);//abefPPPg
//要求字符串找那个的PPP替换AAA（不会改变原来的）
NSString *str1 = [str stringByReplacingOccurrencesOfString:@"PPP" withString:@"AAA"];
NSLog(@"%@",str);//abefPPPg
NSLog(@"%@",str1);//abefAAAg
//OccurrencesOfString:需要替换的字符串
//withString:用什么替换
//options:替换时的搜索方式
//range:搜索范围
//返回值：替换了多少个
NSMutableString *strM = [NSMutableString stringWithFormat:@"abcdefgbc"];
NSUInteger count = [strM replaceOccurrencesOfString:@"bc" withString:@"KKK" options:0 range:NSMakeRange(0, strM.length)];
NSLog(@"%@",strM);//aKKKdefgKKK
NSLog(@"%lu",(unsigned long)count);//2
