NSSrting的几种经常使用的使用方法

1.创建NSString字符串

NSString 与 char* 最大的差别就是 NSString是一个objective对象,而char* 是一个字节数组。

@+" 字符串 " 这个符号为objective-c NSString 字符串常量的标准使用方法。char* 创建的时候 无需加入@

- (void)viewDidLoad
    [super viewDidLoad];
    //经典的字符串赋值
    NSString *str0 = @"my name is justcoding !";
    //字符串格式化合并分别包含
    //NSString*类型 int类型 char*类型
    NSString *str1 = [NSString stringWithFormat:@"我的名字：%@ 我的年龄：%d 我的邮箱：%s",@"justcoding", 25,"justcoding@gmail.com"];
    //字符串赋值 參数中仅仅能够写一个字符串 和第一种非常像
    NSString *str2 = [NSString stringWithString:@"我是字符串"];
    //字符串转换为utf-8格式 參数为char*类型
    NSString *str3 = [NSString stringWithUTF8String:"字符串转换utf-8格式"];
    //字符串合并
    int i  = 100;
    char*c = "xuanyusong";
    NSString *temp = @"我是暂时字符串";
    //在字符串temp的基础继续加入 int i 与 char* c 组成一个新的字符串
    NSString *str4 = [temp stringByAppendingFormat:@"整型： %d 字符型 ：%s",i,c];
    //在字符串temp的基础继续加入temp 并组成一个新的字符串
    NSString *str5 = [temp stringByAppendingString:temp];
    //字符串输出
    NSLog(@"str0 = %@", str0);
    NSLog(@"str1 = %@", str1);
    NSLog(@"str2 = %@", str2);
    NSLog(@"str3 = %@", str3);
    NSLog(@"str4 = %@", str4);
    NSLog(@"str5 = %@", str5);
- (void)viewDidLoad
{
    [super viewDidLoad];

    //经典的字符串赋值
    NSString *str0 = @"my name is justcoding !";

    //字符串格式化合并分别包含
    //NSString*类型 int类型 char*类型
    NSString *str1 = [NSString stringWithFormat:@"我的名字：%@ 我的年龄：%d 我的邮箱：%s",@"justcoding", 25,"justcoding@gmail.com"];

    //字符串赋值 參数中仅仅能够写一个字符串 和第一种非常像
    NSString *str2 = [NSString stringWithString:@"我是字符串"];

    //字符串转换为utf-8格式 參数为char*类型
    NSString *str3 = [NSString stringWithUTF8String:"字符串转换utf-8格式"];

    //字符串合并
    int i  = 100;
    char*c = "xuanyusong";
    NSString *temp = @"我是暂时字符串";

    //在字符串temp的基础继续加入 int i 与 char* c 组成一个新的字符串
    NSString *str4 = [temp stringByAppendingFormat:@"整型： %d 字符型 ：%s",i,c];

    //在字符串temp的基础继续加入temp 并组成一个新的字符串
    NSString *str5 = [temp stringByAppendingString:temp]; 

    //字符串输出
    NSLog(@"str0 = %@", str0);
    NSLog(@"str1 = %@", str1);
    NSLog(@"str2 = %@", str2);
    NSLog(@"str3 = %@", str3);
    NSLog(@"str4 = %@", str4);
    NSLog(@"str5 = %@", str5);

}
2.字符串的遍历 

每个字符串事实上是由若干个char字符组成。字符串的遍历实际上就是将字符串中的每个字符提取出来。

- (void)viewDidLoad
    [super viewDidLoad];
    //经典的字符串赋值
    NSString *str = @"YUSONGMOMO";
    //字符串的长度
    int count = [str length];
    NSLog(@"字符串的长度是%d",count);
    //遍历字符串中的每个字符
    for(int i =0; i < count; i++)
        char c = [str characterAtIndex:i];
        NSLog(@"字符串第 %d 位为 %c",i,c);
- (void)viewDidLoad
{
    [super viewDidLoad];

    //经典的字符串赋值
    NSString *str = @"YUSONGMOMO";

    //字符串的长度
    int count = [str length];

    NSLog(@"字符串的长度是%d",count);

    //遍历字符串中的每个字符
    for(int i =0; i < count; i++)
    {
        char c = [str characterAtIndex:i];
        NSLog(@"字符串第 %d 位为 %c",i,c);
    }

}

3.字符串的比較 

isEqualToString 比較字符串是否全然相等。大写和小写不一样也无法全然匹配。

hasPrefixe 匹配字符串头

haSuffix     匹配字符串的尾巴

- (void)viewDidLoad
    [super viewDidLoad];
    NSString *str0 = @"justcoding";
    NSString *str1 = @"justcoding";
    //字符串全然相等比較
    if([str0 isEqualToString:str1])
        NSLog(@"字符串全然相等");
    //字符串以开头比較
    if([str0 hasPrefix:@"just"])
        NSLog(@"字符串str0以just开头");
    //字符串以结尾比較
    if([str1 hasSuffix:@"coding"])
        NSLog(@"str1字符串以coding结尾");
- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *str0 = @"justcoding";
    NSString *str1 = @"justcoding";

    //字符串全然相等比較
    if([str0 isEqualToString:str1])
    {
        NSLog(@"字符串全然相等");
    }

    //字符串以开头比較
    if([str0 hasPrefix:@"just"])
    {
        NSLog(@"字符串str0以just开头");
    }

    //字符串以结尾比較
    if([str1 hasSuffix:@"coding"])
    {
        NSLog(@"str1字符串以coding结尾");
    }
}

//isEqualToString方法
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 isEqualToString:astring02];
NSLog(@"result:%d",result);
//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)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
//NSOrderedSame 推断两者内容是否同样
//compare方法(comparer返回的三种值)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
//NSOrderedSame 推断两者内容是否同样

NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
NSLog(@"result:%d",result);
//NSOrderedAscending 推断两对象值的大小(按字母顺序进行比較，astring02大于astring01为真)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
NSLog(@"result:%d",result);
//NSOrderedAscending 推断两对象值的大小(按字母顺序进行比較。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 推断两对象值的大小(按字母顺序进行比較，astring02小于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 推断两对象值的大小(按字母顺序进行比較，astring02小于astring01为真)

//不考虑大 小写比較字符串1
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
//NSOrderedDescending推断两对象值的大小(按字母顺序进行比較。astring02小于astring01为 真)
//不考虑大 小写比較字符串1
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
//NSOrderedDescending推断两对象值的大小(按字母顺序进行比較，astring02小于astring01为 真)

//不考虑大写和小写比較字符串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:不区分大写和小写比較 NSLiteralSearch:进行全然比較。区分大写和小写 NSNumericSearch:比較字符串的字符个数，而不是字符值。
//不考虑大写和小写比較字符串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:不区分大写和小写比較 NSLiteralSearch:进行全然比較，区分大写和小写 NSNumericSearch:比較字符串的字符个数，而不是字符值。
推断的方法能够利用 NSString 类别中 caseInsensitiveCompare: 所回传 -1、0 或是 1 的数值，判定两个字串之间得排序关系。其程式玛例如以下。

NSString *string = @"0";
 NSComparisonResult result = [string caseInsensitiveCompare:@"A"];
 switch (result) {
 case NSOrderedAscending:
 NSLog(@"升幂");
 break;
 case NSOrderedSame:
 NSLog(@"忽略大写和小写同样的字串");
 break;
 case NSOrderedDescending:
 NSLog(@"降幂");
 break;
 default:
 NSLog(@"无法判定");
 break;
NSString *string = @"0";
 NSComparisonResult result = [string caseInsensitiveCompare:@"A"];

 switch (result) {
 case NSOrderedAscending:
 NSLog(@"升幂");
 break;

 case NSOrderedSame:
 NSLog(@"忽略大写和小写同样的字串");
 break;

 case NSOrderedDescending:
 NSLog(@"降幂");
 break;

 default:
 NSLog(@"无法判定");
 break;
 }

4. 文件字符串操作（读写）

//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]; //astring=nil;
//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]; //astring=nil;

//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];  //astring=nil;
//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];  //astring=nil;

* ios5 不支持release iOS应用开发：什么是ARC？

//扩展路径
NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
//扩展路径
NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
//文件扩展名
NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);
//文件扩展名
NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);

5. 字符串的截取和大写和小写

//改变字符串的大写和小写
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
//改变字符串的大写和小写
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

Java代码
- (void)viewDidLoad
    [super viewDidLoad];
    NSString *str0 = @"中文my name is xuanyusong";
    //截取字符串起始点到index为4之间的内容
    NSString * to = [str0 substringToIndex:4];
    NSLog(@"to = %@",to);
    //截取字符index为2 到结尾之间的内容
    NSString * from = [str0 substringFromIndex:2];
    NSLog(@"from = %@",from);
    //设置截取字符串的范围
    //从第二位開始,长度为十
    NSRange rang = NSMakeRange(2, 10);
    NSString * strRang = [str0 substringWithRange:rang];
    NSLog(@"rang = %@",strRang);
    //设置字符串首字母大写
    NSLog(@"str0首字母大写:%@",[str0 capitalizedString]);
    //设置字符串所有内容为大写
    NSLog(@"str0大写:%@",[str0 uppercaseString]);
    //设置字符所有内容为小写
    NSLog(@"str0小写:%@",[str0 lowercaseString]);
- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *str0 = @"中文my name is xuanyusong";

    //截取字符串起始点到index为4之间的内容
    NSString * to = [str0 substringToIndex:4];

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

    //截取字符index为2 到结尾之间的内容
    NSString * from = [str0 substringFromIndex:2];

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

    //设置截取字符串的范围
    //从第二位開始,长度为十
    NSRange rang = NSMakeRange(2, 10);
    NSString * strRang = [str0 substringWithRange:rang];
    NSLog(@"rang = %@",strRang);

    //设置字符串首字母大写
    NSLog(@"str0首字母大写:%@",[str0 capitalizedString]);
    //设置字符串所有内容为大写
    NSLog(@"str0大写:%@",[str0 uppercaseString]);
    //设置字符所有内容为小写
    NSLog(@"str0小写:%@",[str0 lowercaseString]);

}

6.搜索字符串与替换字符串

- (void)viewDidLoad
    [super viewDidLoad];
    NSString *str0 = @"中文my name is xuanyusong";
    NSString *temp = @"is";
    NSRange rang = [str0 rangeOfString:temp];
    NSLog(@"搜索的字符串在str0中起始点的index 为 %d", rang.location);
    NSLog(@"搜索的字符串在str0中结束点的index 为 %d", rang.location + rang.length);
    //将搜索中的字符串替换成为一个新的字符串
    NSString *str = [str0 stringByReplacingCharactersInRange:rang withString:@"哇咔咔卡卡咔"];
    NSLog(@"替换后字符串为%@", str);
    //将字符串中" " 所有替换成 *
    str = [str0 stringByReplacingOccurrencesOfString :@" " withString:@"@"];
    NSLog(@"替换后字符串为%@", str);
- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *str0 = @"中文my name is xuanyusong";
    NSString *temp = @"is";
    NSRange rang = [str0 rangeOfString:temp];

    NSLog(@"搜索的字符串在str0中起始点的index 为 %d", rang.location);
    NSLog(@"搜索的字符串在str0中结束点的index 为 %d", rang.location + rang.length);

    //将搜索中的字符串替换成为一个新的字符串
    NSString *str = [str0 stringByReplacingCharactersInRange:rang withString:@"哇咔咔卡卡咔"];
    NSLog(@"替换后字符串为%@", str);

    //将字符串中" " 所有替换成 *
    str = [str0 stringByReplacingOccurrencesOfString :@" " withString:@"@"];
    NSLog(@"替换后字符串为%@", str);

}

拓展：使用以下这种方法总体替换字符串还能够设置替换的区域。 

stringByReplacingOccurrencesOfString:(NSString *)withString:(NSString *) options:(NSStringCompareOptions) range:(NSRange)

7.字符串尾部加入

使用alloc在内存中创建字符串对象后边能够动态的操作这个字符串，改动与加入等。

appendstring 方法：向字符串尾部加入一个字符串。

appendFormat方法：向字符串尾部加入多个类型的字符串。能够加入随意数量与类型的字符串。

- (void)viewDidLoad
    [super viewDidLoad];
    NSMutableString * str = [[NSMutableString alloc] init];
    //加入普通的字符串
    [str appendString:@"aaa"];
    //加入字符串 整型 字符型
    [str appendFormat:@"我的名字：%@ 我的年龄：%d 我的邮箱：%s",@"justcoding", 25,"justcoding@gmail.com"];
    NSLog(@"str = %@",str);
- (void)viewDidLoad
{
    [super viewDidLoad];

    NSMutableString * str = [[NSMutableString alloc] init];

    //加入普通的字符串
    [str appendString:@"aaa"];

    //加入字符串 整型 字符型
    [str appendFormat:@"我的名字：%@ 我的年龄：%d 我的邮箱：%s",@"justcoding", 25,"justcoding@gmail.com"];

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

}
8. 字符串中删除元素

stringWithString 方法：用于创建字符串初始化赋值

rangeOfString方法：传入字符串返回一个在该字符串中的范围 也能够写 NSMakeRange(0, 3) 意思是范围在字符串0位到第3位

deleteCharactersInRange:删除字符串 參数为Range 就是删除的范围。

- (void)viewDidLoad
    [super viewDidLoad];
    //创建字符串
    NSMutableString *str = [NSMutableString stringWithString:@"justcoding is best!"];
    //删除字符串中含"justcoding"的字符
    [str deleteCharactersInRange: [str rangeOfString: @"justcoding"]];
    NSLog(@"str = %@",str);
- (void)viewDidLoad
{
    [super viewDidLoad];

    //创建字符串
    NSMutableString *str = [NSMutableString stringWithString:@"justcoding is best!"];

    //删除字符串中含"justcoding"的字符
    [str deleteCharactersInRange: [str rangeOfString: @"justcoding"]];    

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

}

9. 字符串插入

stringWithString 方法：用于创建字符串初始化赋值

insertString方法：第一个參数 插入的字符串对象， 第二个參数 插入的位置。

- (void)viewDidLoad
    [super viewDidLoad];
    //创建字符串
    NSMutableString *str = [NSMutableString stringWithString:@"justcoding is"];
    //在str第10位插入字符串
    [str insertString:@"best man" atIndex:10];
    NSLog(@"str = %@",str);
- (void)viewDidLoad
{
    [super viewDidLoad];

    //创建字符串
    NSMutableString *str = [NSMutableString stringWithString:@"justcoding is"];

    //在str第10位插入字符串
    [str insertString:@"best man" atIndex:10];

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

}

10. 字符串拷贝

- (void)viewDidLoad
    [super viewDidLoad];
    //创建字符串
    NSMutableString *str1 = [NSMutableString stringWithString: @"字符串1"];
    NSMutableString *str2;
    //字符串赋值
    str2 = str1;
    [str2 appendString: @" 和字符串2"];
    NSLog (@"str1 = %@", str1);
    NSLog (@"str2 = %@", str2);
- (void)viewDidLoad
{
    [super viewDidLoad];

    //创建字符串
    NSMutableString *str1 = [NSMutableString stringWithString: @"字符串1"];
    NSMutableString *str2;

    //字符串赋值
    str2 = str1;

    [str2 appendString: @" 和字符串2"];

    NSLog (@"str1 = %@", str1);

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

为什么给str2加入数据后 str1的数据也改变了？这就是指针的魅力所在，由于我们操作的是指针，str2 = str1  意思是两个指针同一时候指向一块内存，那么str2指向的内存内容改变以后str1当然跟着改变了。

11. 字符串与指定类型转换

假设转换的參数非法的话不会抛出异常，好比用中文去转整型。

不会报错 可是转换结果为 0  。默认值。

- (void)viewDidLoad
    [super viewDidLoad];
    //字符串转整型
    NSString *str0 = @"1121";
    //NSString *str0 = @"中国";
    //把字符串强转成整型
    int i = [str0 intValue];
    NSLog (@"转换后：%i", i);
    //字符串转interger
      NSString *str1 = @"1985";
    // NSString *str1 = @"中国";
    //把字符串强转成interger
    NSInteger ii = [str1 integerValue];
    NSLog (@"转换后：%i", ii);
    //字符串转double
    NSString *str2 = @"3.145926";
    //NSString *str2 = @"中国";
    //把字符串强转成double
    double d = [str2 doubleValue];
    NSLog (@"转换后：%f", d);
    //字符串转float
    NSString *str3 = @"3.145926";
     //NSString *str3 = @"中国";
    //把字符串强转成float
    double f = [str3 floatValue];
    NSLog (@"转换后：%f", f);
- (void)viewDidLoad
{
    [super viewDidLoad];

    //字符串转整型
    NSString *str0 = @"1121";
    //NSString *str0 = @"中国";

    //把字符串强转成整型
    int i = [str0 intValue];

    NSLog (@"转换后：%i", i); 

    //字符串转interger
      NSString *str1 = @"1985";
    // NSString *str1 = @"中国";

    //把字符串强转成interger
    NSInteger ii = [str1 integerValue];

    NSLog (@"转换后：%i", ii); 

    //字符串转double
    NSString *str2 = @"3.145926";
    //NSString *str2 = @"中国";

    //把字符串强转成double
    double d = [str2 doubleValue];

    NSLog (@"转换后：%f", d); 

    //字符串转float
    NSString *str3 = @"3.145926";
     //NSString *str3 = @"中国";
    //把字符串强转成float
    double f = [str3 floatValue];

    NSLog (@"转换后：%f", f); 

}