NSString

// —————————NSString

// NSString

//1.初始化:直接字符串、格式化字符串、文件读取内容初始化

NSString *str1 = @"hello world!";

NSString *str2 = [NSString stringWithFormat:@"start to printf: %@", str1];

NSString *str3 = [[NSString alloc] initWithContentsOfFile:@"/user/document/test.txt" encoding:NSUTF8StringEncoding error:nil];

// 字符串写入文件

[str1 writeToFile:@"/user/document/test.txt" atomically:YES];

// 字符串大写、小写、首字母大写

str1 = [str1 uppercaseString];

str1 = [str1 lowercaseString];

str1 = [str1 capitalizedString];

//字符串截取

str2 = [str1 substringFromIndex:5];

NSLog(@"string = %@", str2);

str2 = [str1 substringToIndex:5];

NSLog(@"string = %@", str2);

str2 = [str1 substringWithRange:NSMakeRange(0, 7)];

NSLog(@"string = %@", str2);

// 字符串是否以另一字符串开头或结尾

BOOL isStart = [str1 hasPrefix:@"hello"];

NSLog(@"isStart is : %i", isStart);

BOOL isEnd = [str1 hasSuffix:@"world!"];

NSLog(@"isEnd is : %i", isEnd);

// 获取文件后缀名

NSString *filePath = @"/document/test.txt";

NSString *ext = [filePath pathExtension];

NSLog(@"ext is : %@", ext);

// 字符串转整形

NSString *value = @"100";

int va = [value intValue];

NSLog(@"va is : %i", va);

// 字符串替换

str1 = [str1 stringByReplacingOccurrencesOfString:@"hello" withString:@"bye bye"];

// 字符串转整

int intVal = [str1 intValue];

NSLog(@"str to int : intVal= %i", intVal);

str1 = [[NSNumber numberWithInteger:intVal] stringValue];

NSLog(@"int to str = %@", str1);

// 字符串分割

NSString *splitStr = @"test1;test2;test3;test4";

NSArray *array = [splitStr componentsSeparatedByString:@";"];

NSLog(@"%@", array);

// 可变字符串

NSMutableString *mulStr = [[NSMutableString alloc] initWithCapacity:1];

[mulStr appendString:@"test1"];

[mulStr appendFormat:@"test2"];

[mulStr insertString:@";" atIndex:5];

[mulStr replaceCharactersInRange:NSMakeRange(0, 4) withString:@"replace test"];

[mulStr deleteCharactersInRange:NSMakeRange(0, 4)];

// 查找字符串包含

NSRange range = [mulStr rangeOfString:@"test"];

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

NSLog(@"mulStr is : %@", mulStr);

// 字符串比较  小于：-1 等于：0 大于：1

NSString *comStr1 = @"bbc";

NSString *comStr2 = @"bbc";

NSComparisonResult result = [comStr1 compare:comStr2];

NSLog(@"result=%ld", result);