iOS NSString的常用用法(史上最全)

阿新 • • 發佈：2019-02-12

NSString *str1 = @"BeiJing";
    NSString *str2 = @"beijing";

    //全部轉為大寫
    NSLog(@"%@",[str1 uppercaseString]);

    //全部轉為小寫
    NSLog(@"%@",[str1 lowercaseString]);

    //首字母大寫
    NSLog(@"%@",[str1 capitalizedString]);

    //比較兩個字串內容是否相同
    BOOL b =[str1 isEqualToString:str2];

    //5.兩個字串內容比較
    //NSOrderedAscending    右邊 > 左邊
    //NSOrderedSame         內容相同
    //NSOrderedDescending   左邊 > 右邊
    NSComparisonResult result = [str1 compare:str2];
    if (result == NSOrderedAscending) {
        NSLog(@"右邊 > 左邊");
    }else if(result == NSOrderedSame){
        NSLog(@"內容相同");
    }else if (result == NSOrderedDescending){
        NSLog(@"左邊 > 右邊");
    }

    //忽略大小寫進行比較，返回值與compare一樣
    result = [str1 caseInsensitiveCompare:str2];
    if (result == NSOrderedAscending) {
        NSLog(@"右邊 > 左邊");
    }else if(result == NSOrderedSame){
        NSLog(@"內容相同");
    }else if (result == NSOrderedDescending){
        NSLog(@"左邊 > 右邊");
    }

    //判斷字串是否以指定字串開頭
    [str1 hasPrefix:@"aaa"];
    //判斷字串是否以指定字串結尾
    [str1 hasSuffix:@"aaa"];

    //判斷字串是否包含指定字串，返回位置和長度
    NSRange range = [@"123456" rangeOfString:@"456"];
    NSLog(@"%@", NSStringFromRange(range));

    //反向搜尋
    range = [@"123456456qweasasd456" rangeOfString:@"456" options:NSBackwardsSearch];
    NSLog(@"%@",NSStringFromRange(range));

    //指定範圍進行搜尋
    range = NSMakeRange(0, 9);
    range = [@"123456456qweasasd456" rangeOfString:@"456" options:NSBackwardsSearch range:range];
    NSLog(@"%@",NSStringFromRange(range));

    //字串的擷取
    NSString *str = @"123456789";
    NSLog(@"%@",[str substringFromIndex:3]);
    NSLog(@"%@",[str substringToIndex:6]);
    NSLog(@"%@",[str substringWithRange:NSMakeRange(3, 3)]);

    //用指定字串分割字串，返回一個數組
    NSArray *array = [@"1,2,3,4,5,6" componentsSeparatedByString:@","];
    NSLog(@"%@",array);

    //將陣列中的字串組合成一個檔案路徑
    NSMutableArray *components = [NSMutableArray array];
    [components addObject:@"Users"];
    [components addObject:@"CentralPerk"];
    [components addObject:@"Desktop"];
    NSString *path = [NSString pathWithComponents:components];
    NSLog(@"%@",path); //Users/CentralPerk/Desktop

    //將一個路徑分割成一個數組
    NSArray *array1 = [path pathComponents];
    NSLog(@"%@",array1);

    //判斷是否為絕對路徑(依據：是否以'/'開始)
    path = @"/Users/CentralPerk/Desktop";
    NSLog(@"%i",[path isAbsolutePath]);

    //獲取最後一個目錄
    NSLog(@"%@",[path lastPathComponent]);

    //刪除最後一個目錄
    NSLog(@"%@",[path stringByDeletingLastPathComponent]);

    //拼接一個目錄
    NSLog(@"%@",[path stringByAppendingPathComponent:@"aaa"]);   ///Users/CentralPerk/Desktop/aaa
    NSLog(@"%@",[path stringByAppendingString:@"aaa"]);      ///Users/CentralPerk/Desktopaaa
    NSLog(@"%@",[path stringByAppendingFormat:@"%@%@",@"b",@"c"]); ///Users/CentralPerk/Desktopbc

    //拓展名出來
    //獲取拓展名,不帶.
    NSString *str3 = @"Users/CentralPerk/Desktop/test.txt";
    NSLog(@"%@",[str3 pathExtension]);
    //新增拓展名,不需要帶.
    NSLog(@"%@",[str3 stringByAppendingPathExtension:@"mp3"]);
    //刪除拓展名,帶.一塊刪除
    NSLog(@"%@",[str3 stringByDeletingPathExtension]);

    //字串轉為 int double float
    NSString *str4 = @"123";
    NSLog(@"%i",[str4 intValue]);
    NSLog(@"%zi",[str4 length]);

    //取出指定位置的字元
    unichar c = [str4 characterAtIndex:2];
    NSLog(@"%c",c);

    //轉為C語言的字串
    const char *s = [str4 UTF8String];
    NSLog(@"%s",s);

    //去掉兩端的空格
    [str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    //去掉多餘的空格
    NSString *str = @"    this     is a    test    .   ";
    NSCharacterSet *whitespaces = [NSCharacterSet whitespaceCharacterSet];
    NSPredicate *noEmptyStrings = [NSPredicate predicateWithFormat:@"SELF != ''"];
    NSArray *parts = [str componentsSeparatedByCharactersInSet:whitespaces];
    NSArray *filteredArray = [parts filteredArrayUsingPredicate:noEmptyStrings];
    str = [filteredArray componentsJoinedByString:@" "];

    //去掉所有空格
    [str stringByReplacingOccurrencesOfString:@" " withString:@""]








    //1、建立常量字串。
    NSString *astring = @"This is a String!";


    //2、建立空字串，給予賦值。
    NSString *astring = [[NSString alloc] init];
    astring = @"This is a String!";
    NSLog(@"astring:%@",astring);

    //
    NSString *astring = [[NSString alloc] init];
    NSLog(@"0x%.8x", astring);

[email protected]"This is a String!";
    NSLog(@"0x%.8x", astring);
    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);


    //4、用標準c建立字串:initWithCString方法
    char *Cstring = "This is a String!";
    NSString *astring = [[NSString alloc] initWithCString:Cstring];
    NSLog(@"astring:%@",astring);

    //5、建立格式化字串:佔位符（由一個%加一個字元組成）
    int i = 1;
    int j = 2;
    NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
    NSLog(@"astring:%@",astring);

    //6、建立臨時字串
    NSString *astring;
    astring = [NSString stringWithCString:"This is a temporary string"];
    NSLog(@"astring:%@",astring);



    //7、從檔案建立字串
    NSString *path = [[NSBundlemainBundle] pathForResource:@"astring.text"ofType:nil];
    NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
    NSLog(@"astring:%@",astring);


    //8、用字串建立字串，並寫入到檔案
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
    NSLog(@"astring:%@",astring);
    NSString *path = @"astring.text";//注：此路徑path只只是示意，真實路徑並非如此
    [astring writeToFile: path atomically: YES];


    //9、用C比較:strcmp函式
    char string1[] = "string!";
    char string2[] = "string!";
    if(strcmp(string1, string2) == 0){
        NSLog(@"1");
    }



    //10、isEqualToString方法
    NSString *astring01 = @"This is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 isEqualToString:astring02];
    NSLog(@"result:%d",result);



    //11、compare方法(comparer返回的三種值)
    NSString *astring01 = @"This is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 compare:astring02] == NSOrderedSame;    //NSOrderedSame判斷兩者內容是否相同
    NSLog(@"result:%d",result);
    //
    NSString *astring01 = @"This is a String!";
    NSString *astring02 = @"this is a String!";
    BOOL result = [astring01 compare:astring02] == NSOrderedAscending;    //NSOrderedAscending判斷兩物件值的大小(按字母順序進行比較，astring02大於astring01為真)
    NSLog(@"result:%d",result);

    //
    NSString *astring01 = @"this is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 compare:astring02] == NSOrderedDescending;    //NSOrderedDescending判斷兩物件值的大小(按字母順序進行比較，astring02小於astring01為真)
    NSLog(@"result:%d",result);




    //12、不考慮大小寫比較字串
    //1.
    NSString *astring01 = @"this is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 caseInsensitiveCompare:astring02] == NSOrderedSame;    //NSOrderedDescending判斷兩物件值的大小(按字母順序進行比較，astring02小於astring01為真)
    NSLog(@"result:%d",result);

    //2.
    NSString *astring01 = @"this is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 compare:astring02

                             options:NSCaseInsensitiveSearch | NSNumericSearch] == NSOrderedSame;    //NSCaseInsensitiveSearch:不區分大小寫比較 NSLiteralSearch:進行完全比較，區分大小寫 NSNumericSearch:比較字串的字元個數，而不是字元值。
    NSLog(@"result:%d",result);


    //13、輸出大寫或者小寫字串
    NSString *string1 = @"A String";
    NSString *string2 = @"String";
    NSLog(@"string1:%@",[string1 uppercaseString]);//大寫
    NSLog(@"string2:%@",[string2 lowercaseString]);//小寫
    NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小



    //14、-rangeOfString: //查詢字串某處是否包含其它字串
    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);



    //15、-substringToIndex: 從字串的開頭一直擷取到指定的位置，但不包括該位置的字元
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringToIndex:3];
    NSLog(@"string2:%@",string2);



    //16、-substringFromIndex: 以指定位置開始（包括指定位置的字元），幷包括之後的全部字元
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringFromIndex:3];
    NSLog(@"string2:%@",string2);



    //17、-substringWithRange: //按照所給出的位置，長度，任意地從字串中擷取子串
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
    NSLog(@"string2:%@",string2);



    //18、-stringWithCapacity: //按照固定長度生成空字串
    NSMutableString *String;
    String = [NSMutableString stringWithCapacity:40];


    //19、-appendString: and -appendFormat: //把一個字串接在另一個字串的末尾
    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);


    //20、-insertString: atIndex: //在指定位置插入字串
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 insertString:@"Hi! " atIndex:0];
    NSLog(@"String1:%@",String1);


    //21、-setString: 替換字串
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 setString:@"Hello Word!"];
    NSLog(@"String1:%@",String1);


    //22、-replaceCharactersInRange: withString: //用指定字串替換字串中某指定位置、長度的字串
    NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
    [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];
    NSLog(@"String1:%@",String1);


    //23、-hasPrefix: //檢查字串是否以另一個字串開頭
    NSString *String1 = @"NSStringInformation.txt";
    [String1 hasPrefix:@"NSString"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");
    [String1 hasSuffix:@".txt"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");


    //24、擴充套件路徑
    NSString *Path = @"~/NSData.txt";
    NSString *absolutePath = [Path stringByExpandingTildeInPath];
    NSLog(@"absolutePath:%@",absolutePath);
    NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);



    //25、副檔名
    NSString *Path = @"~/NSData.txt";
    NSLog(@"Extension:%@",[Path pathExtension]);


    //26、剪下字串，按照range的要求，從第幾個開始，剪下的長度為幾
    NSMutableString *a = [[NSMutableString alloc] initWithString:@"123456798"];
    NSLog(@" \n a: %@ \n",a);
    [a deleteCharactersInRange:NSMakeRange(1, 2)];
    NSLog(@" \n a: %@ \n",a);
    //    2011-07-05 20:59:34.169 Q[9069:207]    a: 123456798
    //    2011-07-05 20:59:34.171 Q[9069:207]    a: 1456798

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