Object-c 中字符串总结

//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!"; 
[astring release]; 
NSLog(@"astring:%@",astring); 

//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); 

/*----------------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]; 
/*----------------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]; 
/*----------------比较两个字符串----------------*/ 
//用C比较: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。 
/*----------------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 
/*---------------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]; 
/*----------------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); 
//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]); 
/******************************************************************************************* 
NSMutableString 
*******************************************************************************************/ 
/*---------------给字符串分配容量----------------*/ 
//stringWithCapacity: 
NSMutableString *String; 
String = [NSMutableString stringWithCapacity:40]; 
/*---------------在已有字符串后面添加字符----------------*/ 
//appendString: and appendFormat: 
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); 
*/ 
/*--------在已有字符串中按照所给出范围和长度删除字符------*/ 
/* 
//deleteCharactersInRange: 
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; 
[String1 deleteCharactersInRange:NSMakeRange(0, 5)]; 
NSLog(@"String1:%@",String1); 
/*--------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); 
/*--------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); 
/*--------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); 
/*-------------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;