Object-c 中字符串NSString、NSMutableString总结

    // 参考：http://www.myexception.cn/mobile/455287.html
    // NSString.html 的官方文档介绍：
    // https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html
    
    //一、NSString 内容不变，固定字符串
    //1、创建常量字符串。
    NSString *astring = @"This is a String!";
    
    //2、创建空字符串，给予赋值。
    NSString *astring = [[NSString alloc] init];
    astring = @"This is a String!";
    [astring release];
    NSLog(@"astring:%@",astring);
    
    //3、在以上方法中，提升速度:initWithString方法
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
    NSLog(@"astring:%@",astring);
    [astring release];
    
    //4、用标准c创建字符串:initWithCString方法
    char *Cstring = "This is a String!";
    NSString *astring = [[NSString alloc] initWithCString:Cstring];
    NSLog(@"astring:%@",astring);
    [astring release];
    
    //5、创建格式化字符串:占位符（由一个%加一个字符组成）
    int i = 1;
    int j = 2;
    NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
    NSLog(@"astring:%@",astring);
    [astring release];
    
    //6、创建临时字符串
    NSString *astring;
    astring = [NSString stringWithCString:"This is a temporary string"];
    NSLog(@"astring:%@",astring);
    
    //7、获取长度
    NSUInteger uLen1 = [astring length];
    NSLog(@"uLen = %lu", uLen1);
    
    //8、获取指定索引处的字符
    NSUInteger index = 0;
    unichar c = [sFormat characterAtIndex:index];
    NSLog(@"The character at index %u of \"%@\" is \'%c\'", index, sFormat, c);
    
    //9、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];
    
    // 10、写字符串到文件:writeToFile方法
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
    NSLog(@"astring:%@",astring);
    NSString *path = @"astring.text";
    [astring writeToFile: path atomically: YES];
    [astring release];
    
    //11、比较两个字符串
    //用C比较:strcmp函数
    char string1[] = "string!";
    char string2[] = "string!";
    if(strcmp(string1, string2) = = 0)
    {
        NSLog(@"1");
    }
    
    //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，升序返回-1，相等返回0，降序返回1)
    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。
    
    //12、改变字符串的大小写
    NSString *string1 = @"A String";
    NSString *string2 = @"String";
    NSLog(@"string1:%@",[string1 uppercaseString]);//大写
    NSLog(@"string2:%@",[string2 lowercaseString]);//小写
    NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小
    
    //13、在串中搜索子串
    NSString *string1 = @"This is a string";
    NSString *string2 = @"string";
    NSRange range = [string1 rangeOfString:string2];
    int location = range.location;
    int leight = range.length;
    NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];
    NSLog(@"astring:%@",astring);
    [astring release];
    
    //14、抽取子串
    //-substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringToIndex:3];
    NSLog(@"string2:%@",string2);
    
    //-substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringFromIndex:3];
    NSLog(@"string2:%@",string2);
    //-substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
    NSLog(@"string2:%@",string2);
    
    //15、扩展路径
    NSString *Path = @"~/NSData.txt";
    NSString *absolutePath = [Path stringByExpandingTildeInPath];
    NSLog(@"absolutePath:%@",absolutePath);
    NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
    
    //16、文件扩展名
    NSString *Path = @"~/NSData.txt";
    NSLog(@"Extension:%@",[Path pathExtension]);
    
    //二、NSMutableString 处理内容可变的字符串
    // 官方文档参考：https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSMutableString_Class/Reference/Reference.html#//apple_ref/occ/cl/NSMutableString
    /*******************************************************************************************
     NSMutableString
     *******************************************************************************************/
    
    /*---------------给字符串分配容量----------------*/
    //1、stringWithCapacity:
    NSMutableString *String;
    String = [NSMutableString stringWithCapacity:40];
    
    //2、在已有字符串后面添加字符
    //appendString: and appendFormat:
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    //[String1 appendString:@", I will be adding some character"];
    [String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];
    NSLog(@"String1:%@",String1);
    
    //3、在已有字符串中按照所给出范围和长度删除字符
    //deleteCharactersInRange:
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 deleteCharactersInRange:NSMakeRange(0, 5)];
    NSLog(@"String1:%@",String1);
    
    //4、在已有字符串后面在所指定的位置中插入给出的字符串
    //-insertString: atIndex:
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 insertString:@"Hi! " atIndex:0];
    NSLog(@"String1:%@",String1);
    
    //5、将已有的空符串换成其它的字符串
    //-setString:
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 setString:@"Hello Word!"];
    NSLog(@"String1:%@",String1);
    
    //6、按照所给出的范围，和字符串替换的原有的字符
    //-setString:
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];
    NSLog(@"String1:%@",String1);
    
    //7、判断字符串内是否还包含别的字符串(前缀，后缀)
    //01：检查字符串是否以另一个字符串开头- (BOOL) hasPrefix: (NSString *) aString;
    NSString *String1 = @"NSStringInformation.txt";
    [String1 hasPrefix:@"NSString"] = = 1 ?NSLog(@"YES") : NSLog(@"NO");
    [String1 hasSuffix:@".txt"] = = 1 ?NSLog(@"YES") : NSLog(@"NO");
    //02：查找字符串某处是否包含其它字符串 - (NSRange) rangeOfString: (NSString *) aString，这一点前面在串中搜索子串用到过;