字符串是程序设计中最常见的数据类型之一。
OC中的字符串NSString
1.NSString是一个对象类型。
2.NSString继承NSObject，具有NSObject的一切特性
3.为了区别C语言的字符串，在双引号前添加了前缀 @
NSString的用法
//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:%@",string);
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:astring02options: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:%@",string);
[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");
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