網上寫的關於字串常用方法的部落格很多，這裡我簡單做了下總結！不喜勿噴哦！

一.建立字串

#import <Foundation/Foundation.h>

//NSString

//建立不可變字串物件的類

//NSMutableString

//建立可變字串物件的類

//OC語言完全相容C語言

//OC字串與C語言字串區別

//1.OC字串是一個字串物件,字串常量需要用@""包含

//2.C語言字串用""包含

//3.C語言的字串以字元的ASCII碼形式儲存

//4.OC中的字串以uicode編碼(萬國碼)形式儲存

//UTF-8(多位元組編碼)

//5.列印OC字串用%@,列印C語言字串用%s

int main(int argc,constchar * argv[]) {

    @autoreleasepool {

        NSString *str1 =@"hello world";//@"hello world"是一個常量字串物件,儲存常量區,不可以被修改

        NSLog(@"str1 = %@", str1);

        //格式化建立字串物件

        //- (instancetype)initWithFormat:(NSString *)format, ...

        NSString *str2 = [[NSString alloc] initWithFormat:@"%s%d%@","hello",123,@"world" ];

        NSLog(@"str2 = %@", str2);

        //用格式化的類方法建立字串物件

        //+ (instancetype)stringWithFormat:(NSString *)format, ...

        NSString *str3 = [NSString stringWithFormat:@"%s%d%@","qiafdn",456,@"ffds"];

        NSLog(@"str3 = %@", str3);

        //用給定的字串物件建立字串物件

        NSString *str4=@"中國教育";

        NSString *str5 = [[NSString alloc] initWithString:str4];

        NSLog(@"str5 = %@", str5);

        //用C的字串建立OC的字串物件

        NSString *str6 = [[NSString alloc] initWithUTF8String:"qifdfdg中國jiaoyu"];

        NSLog(@"str6 = %@", str6);

        NSString *str7 = [[NSString alloc] initWithCString:"我的qifdfg" encoding:NSUTF8StringEncoding];

        NSLog(@"str7 = %@", str7);

        //建立一個空的字串物件 @""

        NSString *str8 = [NSString string];

        NSLog(@"str8 = %@", str8);

        NSString *str9 = [[NSString alloc] init];

        NSLog(@"str9 = %@", str9);

        //跟initWithString相對應

        NSString *str10 = [NSString stringWithString:str7];

        NSLog(@"str10 = %@", str10);

        //跟initWithUTF8String相對應

        NSString *str11 = [NSString stringWithUTF8String:"hello world中國"];

        NSLog(@"str11 = %@", str11);

        //跟initWithCString相對應

        NSString *str12 = [NSString stringWithCString:"zhongguo" encoding:NSUTF8StringEncoding];

        NSLog(@"str12 = %@", str12);

    }

    return0;

}

二.NSString的常用方法

#import <Foundation/Foundation.h>

//NSString

int main(int argc,constchar * argv[]) {

    @autoreleasepool {

        NSString *str1 =@"hello world中國";

        //求字串長度

        NSUInteger len = [str1 length];

        NSLog(@"len = %li", len);

        //獲取字串指定位置的字元

        unichar ch = [str1 characterAtIndex:13];

        NSLog(@"ch = %C", ch);//%C列印unichar字元 %c列印ASCII字元

        //字串提取

        //從傳入下標位置提取子串到字串結束

        NSString *subStr1 = [str1 substringFromIndex:4];

        NSLog(@"subStr1 = %@", subStr1);

        //提取子串到指定位置(不包含下標位置字元)

        NSString *subStr2 = [str1 substringToIndex:7];

        NSLog(@"subStr2 = %@",subStr2);

        //提取指定範圍內的字串

        NSRange range = {6,5};

        NSString *subStr3 = [str1 substringWithRange:range];

        NSLog(@"subStr3 = %@",  subStr3);

        //NSMakeRange();//構建NSRange變數

        NSString *subStr4 = [str1 substringWithRange:NSMakeRange(2,6)];

        NSLog(@"subStr4 = %@", subStr4);

        //字串比較

        NSString *str2 = [NSString stringWithCString:"hallo world中國" encoding:NSUTF8StringEncoding];

        NSString *str3 = [NSString stringWithUTF8String:"hello world中國"];

        NSComparisonResult result = [str2 compare:str3];

        if (result == NSOrderedAscending) {//遞增

            NSLog(@"str2 < str3");

        }

        elseif(result == NSOrderedDescending)//遞減

        {

            NSLog(@"str2 > str3");

        }

        else

        {

            NSLog(@"str2 == str3");

        }

        //以大小寫不敏感方式比較字串

        //[str2 caseInsensitiveCompare:str3];

        //判斷兩個字串是否相等

        //- (BOOL)isEqualToString:(NSString *)aString;

        BOOL ret = [str2 isEqualTo:str3];

        if (ret==YES) {

            NSLog(@"str2 == str3");

        }

        else

        {

            NSLog(@"str2 != str3");

        }

        //判斷字首子串

        //- (BOOL)hasPrefix:(NSString *)aString;

        BOOL ret1 = [@"www.baidu.com" hasPrefix:@"www."];

        NSLog(@"ret1 = %d", ret1);

        //判斷後綴子串

        //- (BOOL)hasSuffix:(NSString *)aString;

        BOOL ret2 = [@"www.hao123.com" hasSuffix:@"com"];

        NSLog(@"ret2 = %d", ret2);

        //判斷是否包含子串(10.10macos)

        BOOL ret3 = [@"hao123" containsString:@"hao"];

        NSLog(@"ret3 = %d", ret3);

        //查詢子串

        NSString *str4 = [[NSString alloc] initWithFormat:@"%s","hello world qidfafddnworldfedffsng"];

        NSRange range1 =[str4 rangeOfString:@"world"];

        if (range1.location == NSNotFound) {//不能查詢對應的子串,返回long型別最大值

            NSLog(@"沒有查詢到字串 notfound = %lu", NSNotFound);

        }

        else

        {

            NSLog(@"location = %lu length = %lu", range1.location, range1.length);

        }

        //倒序查詢子串

        NSRange range2 = [str4 rangeOfString:@"world" options:NSBackwardsSearch];

        NSLog(@"location = %li length = %li", range2.location, range2.length);

        //字串追加

        //並不是直接在原字串的末尾追加字串,而是利用傳入的字串及原字串建立一個新的字串

        NSString *str5 =@"hello";

        NSLog(@"%p", str5);

        str5 = [str5 stringByAppendingString:@"world"];

        NSLog(@"str5 = %@", str5);

        NSLog(@"%p", str5);

        //格式化追加字串

        NSString *str6 =@"qfdfdng";

        str6 = [str6 stringByAppendingFormat:@"%d%s",123,"helloworld"];

        NSLog(@"str6 = %@", str6);

        //把字元換串物件轉換成整型浮點型

        int a = [@"12345" intValue];

        float f = [@"3.14" floatValue];

        NSLog(@"a = %d f = %.2f", a, f);

        //返回公共字首子串

        NSString *str7 = [@"www.baidu.com" commonPrefixWithString:@"www.hao123.com"options:NSLiteralSearch];

        NSLog(@"str7 = %@", str7);

        //大小寫轉換

        //把小寫字母轉換成大寫字母

        NSString *str8 = [@"baidu中國" uppercaseString];

        NSLog(@"str8 = %@", str8);

        //把大寫字母轉換成小寫字母

        NSString *str9 = [@"BaiDU" lowercaseString];

        NSLog(@"str9 = %@", str9);

        //把每個單詞的首字母大寫

        NSString *str10= [@"bai du qian feng" capitalizedString];

        NSLog(@"str10 = %@", str10);

        //字串替換

        //- (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement

        NSString *str11=@"hello world qiafdfnfdg hello world hello hell qdfdfnfdg";

        str11 = [str11 stringByReplacingOccurrencesOfString:@"hello" withString:@"welcome"];

        NSLog(@"str11 = %@", str11);

        //替換指定範圍內的字元

        //- (NSString *)stringByReplacingCharactersInRange:(NSRange)range withString:(NSString *)replacement

        NSString *str12 =@"hello world qianfeng";

        str12 = [str12 stringByReplacingCharactersInRange:NSMakeRange(12,8) withString:@"welcome"];

        NSLog(@"str12 = %@", str12);

        //把OC的字串物件轉換成C字串

        NSLog(@"%s", [@"hello world" UTF8String]);

        //用網址的內容生成OC字串對像

        //- (instancetype)initWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;

        //+ (instancetype)stringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;

        NSURL *url= [[NSURL alloc] initWithString:@"http://www.baidu.com"];

        NSString *urlContent = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];//nil空指標

        NSLog(@"urlContent = %@", urlContent);

        //用檔案的內容生成字串

        //- (instancetype)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;

        //+ (instancetype)stringWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;

        NSString *fileContent = [NSString stringWithContentsOfFile:@"/Users/zhangxueming/Desktop/json.txt"encoding:NSUTF8StringEncoding error:nil];

        NSLog(@"fileContent = %@", fileContent);

    }

    return0;

}

三.NSSMUtableString的常用方法

#import <Foundation/Foundation.h>

//NSMutableString 繼承與NSString

//所有NSString類的方法NSMutableString都可以使用

int main(int argc,constchar * argv[]) {

    @autoreleasepool {

        //建立指定容量大小的可變字串物件

        //+ (NSMutableString *)stringWithCapacity:(NSUInteger)capacity;

        NSMutableString *mulStr1 = [[NSMutableString alloc] initWithCapacity:20];

        NSLog(@"mulStr1 = %@", mulStr1);

        //替換指定範圍內的字元

        //- (void)replaceCharactersInRange:(NSRange)range withString:(NSString *)aString;

        NSMutableString *mulStr2 = [[NSMutableString alloc] initWithString:@"hello world qianfdfsfefdg"];

        [mulStr2 replaceCharactersInRange:NSMakeRange(6,5) withString:@"welcome"];

        NSLog(@"mulStr2 = %@", mulStr2);

        //在指定位置增加字串

        NSMutableString *mulStr3 = [[NSMutableString alloc] initWithFormat:@"夢想中國"];

        [mulStr3 insertString:@"hello world" atIndex:2];

        NSLog(@"mulStr3 = %@", mulStr3);

        //刪除指定範圍內的字元

        NSMutableString *mulStr4 = [NSMutableString stringWithUTF8String:"熱愛hello world中國"];

        [mulStr4 deleteCharactersInRange:NSMakeRange(2,11)];

        NSLog(@"mulStr4 = %@", mulStr4);

        //追加字串

        NSMutableString *mulStr5 = [NSMutableString stringWithString:@"helloworld"];

        [mulStr5 appendString:@"qidffdf"];

        NSLog(@"mulStr5 = %@", mulStr5);

        //格式化追加字串

        NSMutableString *mulStr6 = [NSMutableString stringWithFormat:@"%s%d","hello",12345];

        [mulStr6 appendFormat:@"%.2f%@",3.14,@"world"];

        NSLog(@"mulStr6 = %@", mulStr6);

        //修改字串

        NSMutableString *mulStr7 = [[NSMutableString alloc] initWithString:@"hello world"];

        [mulStr7 setString:@"qifdfdng"];

        NSLog(@"mulStr7 = %@", mulStr7);

    }

    return0;

}