Objective-C学习之旅 第二篇

Objective-C学习之旅 第二篇

Objective-C 字符串处理

//苹果从iOS5开始，就引入了ARC这种内存管理技术，目的就是消除繁琐而容易出错的手工内存管理行为。
//如果项目是ARC的，那么就不能调用原来的retain, release, autorelease，而且dealloc也不再需要内存维护相关的代码。
//也就是说下面的例子中，如果在ARC模式下，就不用[astring release];
/*******************************************************************************************

NSString 不可变字符串

*******************************************************************************************/
/*----------------创建字符串的方法----------------*/
 //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!"];//一般不这么干，比较冗余
NSLog(@"astring:%@",astring);
[astring release];

//4、用标准c创建字符串:initWithCString方法
/*
--NSStringEncoding 中常用的字符编码---------------- 
     NSASCIIStringEncoding 
     NSUTF8StringEncoding 
     NSUnicodeStringEncoding 
*/
char *Cstring = "This is a String!";
NSString *astring = [[NSString alloc] initWithCString:Cstring encoding:NSUTF8StringEncoding];
//该方法需要带上编码规则，新版中不带编码的方法已被弃用
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）、
/*
--常用的替换符-------------- 
　　%@ NSString实例 
　　%d,%D,%i 整数 
　　%u,%U 无符号整数 
　　%x 将无符号整数以十六进制小写字母显示 
　　%X 将无符号整数以十六进制大写字母显示 
　　%f 小数 
　　%c 字符 
　　%s C语言字符串 
　　%% 显示％字符本身 
*/
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" encoding:NSUTF8StringEncoding];
NSLog(@"astring:%@",astring);


/*----------------从文件读取字符串:initWithContentsOfFile方法----------------*/
//可以自己新建一个"astring.text"文件用来测试用，路径获取方法：把文件拖到代码区就可以获取到该文件的绝对路径

NSString *path = @"astring.text";
Ns
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
NSLog(@"astring:%@",astring);
[astring release];

//上面的方法在新版中已被弃用，推荐使用下面的方法
NSString *path = @"astring.text";
NSError *error = nil;
//之所以要用二重指针作为参数,是因为需要为NSError分配内存,有也就是说error本身存取的内容会改变,
//而参数传递属于拷贝传值,必须将指针的地址传过去,通过指针的地址访问指针,才改变的是指针的直.
NSString *astring = [[NSString alloc] initWithContentsOfFile:path
　　　　　　　　　　　　　　 encoding:NSUTF8StringEncodeing error:&error];
if(astring == nil){
　　//Deal with error...
}
//...
[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";
NSError *error = nil; 
[astring writeToFile: path atomically: YES encoding: NSUTF8StringEncoding error:&error];
[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 可变字符串

*******************************************************************************************/

/*---------------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);

/*--------将已有的字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;