IOS NSString 用法详解
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- //NSString 操作均不改变自身值
- //构建字符串
- NSString *szTmp = @"A string"; //直接赋值
- szTmp = nil;
- int n = 5;
- NSString *szMyString = [NSString stringWithFormat:@"The number is %d",n]; //The number is 5
- [szMyString stringByAppendingFormat:@"%d",22]; //附加字符串返回值:The number is 522
- //但是szMyString本身并没有改变,其值依然:The number is 5
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- //长度与索引字符
- NSLog(@"%d",szMyString.length); //字符串长度:15
- NSLog(@"%c",[szMyString characterAtIndex:2]); //返回字符:e
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- //与c字符串相互转换
- printf("%s\n",[szMyString UTF8String]); //转为__strong const char *
- const char *szTmp1 = [szMyString cStringUsingEncoding:NSUTF8StringEncoding];
- printf("%s\n",szTmp1); //转为__strong const char *
- NSLog(@"%@",[NSString stringWithCString:szTmp1 encoding:NSUTF8StringEncoding]); //转为nsstring
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- //字符串写文件
- NSError *error;
- NSString *szPath = [NSHomeDirectory() //应用程序沙盒路径
- stringByAppendingPathComponent:@"Documents/testFile.txt"]; //附加路径地址
- if (![szMyString writeToFile:szPath atomically:YES //atomically:是否是原子访问文件的
- encoding:NSUTF8StringEncoding error:&error]) { //写入成功返回yes 否则no
- NSLog(@"Error writing to file :%@",[error localizedDescription]); //输出错误描述
- return 1;
- }
- NSLog(@"File write success");
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- //文件读字符串
- NSString *szInString = [NSString stringWithContentsOfFile:szPath //读取文件信息
- encoding:NSUTF8StringEncoding error:&error];
- if (!szInString)
- {
- //失败
- }
- NSLog(@"%@",szInString); //成功
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- //字符串转为数组
- NSArray *arrayWord = [szMyString componentsSeparatedByString:@" "]; //有空格的拆分为单词保存
- NSLog(@"%@",arrayWord);
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- //索引子串
- NSString *szSub1 = [szMyString substringToIndex:3]; //0-2,前3个:The
- NSLog(@"%@",szSub1);
- NSString *szSub2 = [szMyString substringFromIndex:4]; //4-尾,去掉前4个:number is 5
- NSLog(@"%@",szSub2);
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- //范围索引
- NSRange range;
- range.location = 4; //从4开始
- range.length = 6; //6个字符
- NSString *szSub3 = [szMyString substringWithRange:range]; //number
- NSLog(@"%@",szSub3);
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- //搜索与替换
- NSRange rangeSearch = [szMyString rangeOfString:@"is 5"]; //搜索
- if (rangeSearch.location != NSNotFound) { //搜索不到是 NSNotFound
- //成功:rangeSearch.location;//位置 rangeSearch.length;//长度
- }
- NSLog(@"%@",[szMyString stringByReplacingCharactersInRange:rangeSearch //用位置匹配替换
- withString:@"isn't 10"]);
- NSString *szReplaced = [szMyString stringByReplacingOccurrencesOfString:@" " withString:@"*"]; //匹配字符串替换
- NSLog(@"%@",szReplaced);
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- //改变大小写
- NSLog(@"%@",[szMyString uppercaseString]); //大写
- NSLog(@"%@",[szMyString lowercaseString]); //小写
- NSLog(@"%@",[szMyString capitalizedString]); //首字母大写
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- //比较字符串
- NSString *sz1 = @"Hello World!";
- NSString *sz2 = @"Hello Mom!";
- if ([sz1 isEqualToString:sz2]) {/*相等*/}
- if ([sz1 hasPrefix:@"Hello"]) {NSLog(@"前部分相等");} //从头开始比较
- if ([sz1 hasSuffix:@"d!"]) {NSLog(@"后部分相等");} //从尾部比较
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- //字符串转换数字
- NSString *szNumber = @"3.14";
- [szNumber intValue];
- [szNumber boolValue];
- [szNumber floatValue];
- [szNumber doubleValue];
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- //可变字符串
- NSMutableString *szMuMyString = [NSMutableString stringWithString:@"Hello"];
- [szMuMyString appendFormat:@"World"]; //字符串,改变自身
- [szMuMyString uppercaseString];
- NSLog(@"%@",szMuMyString);
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