原地址：http://blog.csdn.net/dingkun520wy/article/details/7010270
关于字符串的各种操作，总结一下以便以后复习查找。
内容简要:
1、创建常量字符串。 2、创建空字符串，给予赋值。3、在以上方法中，提升速度:initWithString方法
4、用标准c创建字符串:initWithCString方法。5、创建格式化字符串:占位符（由一个%加一个字符组成）
6、创建临时字符串。7、判断字符串为空。9、是否以”test”开头;是否以”.move”结尾。10、比较两个字符串。
11、声明一个可变字符;长度是40个字符。12、修改可变字符;先声明一个可变字符 myFriend;长度30。
13、在一个字符串后面附加一个新的字符串。14、字符串转换整数值。
15、从文件读取字符串:initWithContentsOfFile方法。16、写字符串到文件:writeToFile方法
17、改变字符串的大小写。18、在串中搜索子串。19、抽取子串。20、扩展路径。21、文件扩展名。
22、在已有字符串后面添加字符。23、在已有字符串中按照所给出范围和长度删除字符。
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。25、将已有的空符串换成其它的字符串。
26、按照所给出的范围，和字符串替换的原有的字符。27、判断字符串内是否还包含别的字符串(前缀，后缀)。
---------------------------------------------------------------------------------------------------------------------
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;