關於字符串的各種操作，總結一下以便以後複習查找。
內容簡要:
1、創建常量字符串。 2、創建空字符串，給予賦值。3、在以上方法中，提升速度:initWithString方法
4、用標準c創建字符串:initWithCString方法。5、創建格式化字符串:佔位符（由一個%加一個字符組成）
6、創建臨時字符串。7、判斷字符串爲空。9、是否以”test”開頭;是否以”.move”結尾。10、比較兩個字符串。
11、聲明一個可變字符;長度是40個字符。12、修改可變字符;先聲明一個可變字符 myFriend;長度30。
13、在一個字符串後面附加一個新的字符串。14、字符串轉換整數值。
15、從文件讀取字符串:initWithContentsOfFile方法。16、寫字符串到文件:writeToFile方法
17、改變字符串的大小寫。18、在串中搜索子串。19、抽取子串。20、擴展路徑。21、文件擴展名。
22、在已有字符串後面添加字符。23、在已有字符串中按照所給出範圍和長度刪除字符。
24、在已有字符串後面在所指定的位置中插入給出的字符串。25、將已有的空符串換成其它的字符串。
26、按照所給出的範圍，和字符串替換的原有的字符。27、判斷字符串內是否還包含別的字符串(前綴，後綴)。
原文地址： http://blog.csdn.net/dingkun520wy/article/details/7010270
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1、創建常量字符串。
NSString *astring = @"This is a String!";
2、創建空字符串，給予賦值。
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、用標準c創建字符串:initWithCString方法
char *Cstring = "This is a String!";
NSString *astring = [[NSString alloc] initWithCString:Cstring];
NSLog(@"astring:%@",astring);
[astring release];
5、創建格式化字符串:佔位符（由一個%加一個字符組成）
int i = 1;
int j = 2;
NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
NSLog(@"astring:%@",astring);
[astring release];
6、創建臨時字符串
NSString *astring;
astring = [NSString stringWithCString:"This is a temporary string"];
NSLog(@"astring:%@",astring);
7、判斷字符串爲空
NSString *urlString = [urlInput stringValue];
if (!urlString) {
NSLog( @”NO INPUT.” );
}
if ([urlString length] == 0 ) {
NSLog( @”NO INPUT.” );
}
9、是否以”test”開頭;是否以”.move”結尾;
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、比較兩個字符串:
strcmp函數
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返回的三種值)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
NSOrderedSame 判斷兩者內容是否相同
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
NSLog(@"result:%d",result);
NSOrderedAscending 判斷兩對象值的大小(按字母順序進行比較，astring02大於astring01爲真)
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;
NSLog(@"result:%d",result);
NSOrderedDescending 判斷兩對象值的大小(按字母順序進行比較，astring02小於astring01爲真)
不考慮大 小寫比較字符串1
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
NSOrderedDescending判斷兩對象值的大小(按字母順序進行比較，astring02小於astring01爲真)
不考慮大小寫比較字符串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:不區分大小寫比較 NSLiteralSearch:進行完全比較，區分大小寫NSNumericSearch:比較字符串的字符個數，而不是字符值。
11、聲明一個可變字符;長度是40個字符;
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、修改可變字符;先聲明一個可變字符 myFriend;長度30;
NSMutableString *myGirlFriend;
myGirlFriend = [NSMutableString stringWithCapacity:30];
//然後給字符加入一些內容;
[myGirlFriend appendString:@"Here are my GF:Carol Sophia Ashley Helen and Yoyo"];
NSLog(@”%@”,myGirlFriend);
//聲名一個變動範圍(NSRange);
NSRange joneRange;
joneRange = [myGirlFriend rangeOfString:@"Helen "];
//下面:就是從myFriend字符中配對,如果有相等的內容就刪除了;
[myGirlFriend deleteCharactersInRange:joneRange];
NSLog(@”%@”,myGirlFriend);
13、在一個字符串後面附加一個新的字符串
NSString *a = @"a";
NSString *b = [a stringByAppendingString:@"b"];//b變量的值爲“ab”
14、字符串轉換整數值
NSString *age = @"36";
if([age intValue]>35){
}
15、從文件讀取字符串:initWithContentsOfFile方法
NSString *path = @"astring.text";
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
NSLog(@"astring:%@",astring);
[astring release];
16、寫字符串到文件: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、改變字符串的大小寫
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
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: 從字符串的開頭一直截取到指定的位置，但不包括該位置的字符
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringToIndex:3];
NSLog(@"string2:%@",string2);
//-substringFromIndex: 以指定位置開始（包括指定位置的字符），幷包括之後的全部字符
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@"string2:%@",string2);
//-substringWithRange: //按照所給出的位置，長度，任意地從字符串中截取子串
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@"string2:%@",string2);
20、擴展路徑
NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
21、文件擴展名
NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);
22、在已有字符串後面添加字符
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給出範圍和長度刪除字符
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 deleteCharactersInRange:NSMakeRange(0, 5)];
NSLog(@"String1:%@",String1);
24、在已有字符串後面在所指定的位置中插入給出的字符串
//-insertString: atIndex:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];
NSLog(@"String1:%@",String1);
25、將已有的空符串換成其它的字符串
//-setString:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 setString:@"Hello Word!"];
NSLog(@"String1:%@",String1);
26、按照所給出的範圍，和字符串替換的原有的字符
//-setString:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];
NSLog(@"String1:%@",String1);
27、判斷字符串內是否還包含別的字符串(前綴，後綴)
//01：檢查字符串是否以另一個字符串開頭- (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：查找字符串某處是否包含其它字符串 - (NSRange) rangeOfString: (NSString *) aString，這一點前面在串中搜索子串用到過;