OC-NSString
4.oc字符串对象常量
各种操作:
1)给不可变字符串对象赋值，获取对应下标的字符：
例如：
NSString * str =@"welcome to qianfeng!";//1.这是一个OC的字符串对象常量； 2.和C语言的字符串写法不同
unichar c = [strcharacterAtIndex:0];//获取索引/下标对应的字符(下标都是从0开始)
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2)创建一个不可变字符串对象，并对其赋值。
//NSString不可变字符串字符串对象的内容不可变
//NSMutableString可变字符串 字符串对象的内容可以改变
方法1：
//1.创建一个字符串对象
NSString * str = [[NSStringalloc]initWithString:@"I love iOS!"];
//str = @"hello"; str指向的对象内容不能改变。但是str这个指针是可以变的
方法2：
//2.创建字符串对象
//代表把C的字符串按照UTF8的编码格式转化为OC的字符串
NSString * str = [[NSStringalloc]initWithUTF8String:"I love iOS!"];
方法3:
//3.创建一个字符串对象
//格式化创建一个字符串对象
//作用1:把int/float数据转化为字符串
NSString *str = [[NSStringalloc]initWithFormat:@"a = %d",a];
NSString *ptr = [[NSStringalloc]initWithFormat:@"%f",3.14];
//作用2:可以实现拼接（另一例子见老师代码OC10）
str =@"I love";
ptr = [[NSStringalloc]initWithFormat:@"%@ you",str];//将you拼接到str内容后，并用ptr指向新的字符串。
NSLog(@"str = %@",str);//str = I love
NSLog(@"ptr = %@",ptr);//ptr = I love you
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3)求字符串的有效长度
NSUInteger l = [str2length];
//或者使用点调用如下:
NSUInteger l = str2.length;//求字符串的长度（字符个数）
另：
unichar c = [str2characterAtIndex:l-1];//OC字符串不包含‘\0’；OC的一切操作不要越界字符串的下标范围是0到l-1
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4)关于两个字符串的比较（注意返回值的定义）
方法一:判断两个字符串是否相等
例如：
NSString * str1 =@"Hello";
NSString * str2 =@"Hello";
//bool a;
//BOOL : signed char YES(1) NO(0)
//判断两个字符串是否相等 相同返回1（YES） 不同返回0（NO）
BOOL ret = [str1 isEqualToString:str2];
方法二:字符串的比较
例如:
//字符串的比较：左边str1 大于右边str2 返回1 小于 返回 -1 相等返回0
NSString * str1 =@"12345";
NSString * str2 =@"54321";
NSComparisonResult retCmp = [str1compare:str2];
NSLog(@"retCmp = %ld",retCmp);
方法三:两字符串不区分大小写进行比较
例如:
NSString * str1 =@"Hello";
NSString * str2 =@"hello";
NSComparisonResultretCmp = [str1 caseInsensitiveCompare:str2];
NSLog(@"retCmp = %ld",retCmp);NSLog(@"retCmp = %ld",retCmp);
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5)字符串查找返回一个范围
NSRange 类中有两个成员变量:location，length；
location是所查找字符串的第一个字符在原字符串中的位置。
length是所查找字符串的长度。
例1:
//字符串查找 返回一个范围
//返回@“to”在@"Welcometobeijing"中的范围；
NSString *str =@"Welcometobeijing";
NSRange range = [strrangeOfString:@"to"];
//找不到返回NSNotFound
if (range.location !=NSNotFound)
{
NSLog(@"range.loc = %lu len = %lu",range.location,range.length);
NSLog(@"range = %@",NSStringFromRange(range));//把（NSRange）转为字符串
}
else
{
NSLog(@"Not found");
}
例2:当字符串中有两个所要查找的子串，默认从前向后查找，且返回第一个所查找到的位置。
NSString *str =@"Welcometobeijingtoqianfeng";
NSRangerange = [str rangeOfString:@"to"];
if (range.location !=NSNotFound)
{
NSLog(@"range.loc = %lu len = %lu",range.location,range.length);//默认返回的是第一找到的范围
NSLog(@"range = %@",NSStringFromRange(range));//把（NSRange）转为字符串
}
else
{
NSLog(@"Not found");
}
例3:当字符串中有两个所要查找的子串，要求从后向前查找，且返回第一个所查找到的位置。
//从后向前查找
range = [strrangeOfString:@"to"options:NSBackwardsSearch];
if (range.location !=NSNotFound)
{
NSLog(@"range = %@",NSStringFromRange(range));
}
else
{
NSLog(@"Not found");
}
例4:在指定范围内，从后向前查找字符串，且返回第一个所查找到的位置。
NSRange range = [strrangeOfString:@"to"options:NSBackwardsSearchrange:NSMakeRange(0,25)];
//注意NSMakeRange的使用，对字符串的操作中会经常使用到。
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6)字符串的提取
方法一:
NSString * str =@"Welcometo1000phone";
NSString * ptr = [strsubstringToIndex:7];//字符串抽取（0<= x <7）不包含下标7；
方法二:
NSString * str =@"Welcometo1000phone";
NSLog(@"ptr = %@",ptr);//从下标9开始抽取到结束包含下标9,即(9<=x<=str.length-1)
方法三:
//在指定范围内抽取
NSString * str =@"Welcometo1000phone";
NSLog(@"ptr = %@",ptr);
ptr = [strsubstringWithRange:NSMakeRange(7,2)];
NSLog(@"ptr = %@",ptr);
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7)把数字串转化为整型数据
例如:
str =@"123";
int a = [strintValue];//把数字串转化为整型数据
NSLog(@"a = %d",a);
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8)把C字符串转化为OC字符串
例子:
char buff1[256] = {};
scanf("%s",buff1);
//把C的转化为OC的
NSString * str1 = [NSStringstringWithUTF8String:buff1];
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5.OC可变字符串对象
什么是可变字符串对象？
答：可变字符串对象的内容可以改变
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1)创建可变字符串对象
例如:
NSMutableString *str = [[NSMutableStringalloc]initWithString:@"helloworld"];
//str指向的对象内容可以改变；
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2)对可变字符串对象的操作:增、删、改
注意:OC中，可变的空间可以动态的增加和减少，不需要手动操作。
-------------增--------------
方法一：
[strinsertString:@"123"atIndex:3];
方法二：
[strappendString:@"iOS"];//追加
-------------删--------------
[strdeleteCharactersInRange:NSMakeRange(2,4)];
-------------改--------------
方法一：
//修改
[strsetString:@"I love her"];
str.string =@"I love her";
方法二：
//替换
NSLog(@"str - %@",str);
[strreplaceCharactersInRange:NSMakeRange(2,4)withString:@"hate"];
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6.把OC字符串转化为C语言的字符串
constchar *p = [strUTF8String];
//或者
char *p = [strUTF8String];
6-13字符串补充
1.判断一个字符串是否是另一个字符串的前缀
方法一:
//返回值是BOOL类型
NSString * str1 =@"1www.baidu.com";
BOOL ret = [str1hasPrefix:@"www."];
方法二:
//返回值是NSRange类型
NSRange range = [str1rangeOfString:@"www."options:NSAnchoredSearchrange:NSMakeRange(0, [str1length]-1)];
//注意：NSAnchoredSearch用法：判断str1在指定范围内，是否把@“www.”作为开始，当设置的范围是从0开始的时候，即变为判断是否是前缀。
通用方法:
NSRange range = [str1rangeOfString:@"www."options:NSAnchoredSearchrange:NSMakeRange(1, [str1length]-1)];
//判断str1从下标1开始的字符串是否以@“www.”作为开头
2.判断一个字符串是否是另一个字符串的后缀
例如:
NSString * str2 =@"1310.doc";
ret = [str2hasSuffix:@".doc"];
NSLog(@"ret = %d",ret);
3.把不可变字符串转化为可变字符串
例如:
NSString * str1 =@"When I was young, I loved a girl on neighbor class.";
NSMutableString * str = [NSMutableStringstringWithString:str1];//把不可变转化为可变
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!";
NSLog(@"astring:%@",astring);
[astring release];
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、判断字符串为空
NSString *urlString = [urlInput stringValue];
if (!urlString) {
NSLog( @”NO INPUT.” );
}
if ([urlString length] == 0 ) {
NSLog( @”NO INPUT.” );
}
9、是否以”test”开头;是否以”.move”结尾;
NSString *fileName = @”test.move”;
if ([fileName hasPrefix:@"test"]) {
NSLog(@”has Test String !”);
}else{
NSLog(@”don’t have Test”);
}
[fileName hasSuffix:@".move"]?NSLog(@”Yes it got a .Mov in its end”):NSLog(@”no it has no .mov string”);
10、比较两个字符串:
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)
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。
11、声明一个可变字符;长度是40个字符;
NSMutableString *myMutableString;
myMutableString = [NSMutableString stringWithCapacity:40];
NSString *myName = @”Leo”;
[myMutableString appendString:@"Hello ,there"];
[myMutableString appendFormat:@" i am %@",myName];
NSLog(@”this is NSMutableString: %@”,myMutableString);
//this is NSMutableString: Hello ,there i am Leo;
12、修改可变字符;先声明一个可变字符 myFriend;长度30;
NSMutableString *myGirlFriend;
myGirlFriend = [NSMutableString stringWithCapacity:30];
//然后给字符加入一些内容;
[myGirlFriend appendString:@"Here are my GF:Carol Sophia Ashley Helen and Yoyo"];
NSLog(@”%@”,myGirlFriend);
//声名一个变动范围(NSRange);
NSRange joneRange;
joneRange = [myGirlFriend rangeOfString:@"Helen "];
//下面:就是从myFriend字符中配对,如果有相等的内容就删除了;
[myGirlFriend deleteCharactersInRange:joneRange];
NSLog(@”%@”,myGirlFriend);
13、在一个字符串后面附加一个新的字符串
NSString *a = @"a";
NSString *b = [a stringByAppendingString:@"b"];//b变量的值为“ab”
14、字符串转换整数值
NSString *age = @"36";
if([age intValue]>35){
}
15、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];
16、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];
17、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
18、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];
19、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);
20、扩展路径
NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
21、文件扩展名
NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);
22、在已有字符串后面添加字符
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);
23、在已有字符串中按照所给出范围和长度删除字符
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 deleteCharactersInRange:NSMakeRange(0, 5)];
NSLog(@"String1:%@",String1);
24、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);
25、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);
26、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);
27、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;