NSString、NSMutableString基本用法

NSString其實是一個對象類型。NSString是NSObject（Cocoa Foundation的基礎對象）的子類

一、NSString的創建

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!";

[astring release];

NSLog(@"astring:%@",astring);

NSString *astring?=?[[NSString alloc] init];

NSLog(@"0x%.8x", astring);

astring=@"This is a String!";

NSLog(@"0x%.8x", astring);

[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:占位符（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、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];

8、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];

二、字符串的比較

1、用C比較:strcmp函數

char string1[]?=?"string!";

char string2[]?=?"string!";

if(strcmp(string1, string2)?=?= 0)

{

NSLog(@"1");

}

2、isEqualToString方法

NSString *astring01?=?@"This is a String!";

NSString *astring02?=?@"This is a String!";

BOOL result =?[astring01 isEqualToString:astring02];

NSLog(@"result:%d",result);

3、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大于astring01為真)

不考慮大小寫比較字符串

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小于astring01為真)

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);

P.S : 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。

三、改寫字符串

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

四、搜索字符串

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];

五、字符串的截取

1.-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);

2.-substringFromIndex:?以指定位置開始（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);

3.-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);

4.截取NSString最后一位符號后的東西

方法1.

NSString *str?=?@"/Users/yangiori/Library/Application Support/iPhone Simulator/5.1/Applicati*****/8724956B-407E-4ACD-BBA6-95C7D033C33D/Documents/content/chapters/8";

NSString *temp1?=?[[str componentsSeparatedByString:@"/"] lastObject];

NSLog(@"%@",temp1);

結果：8

方法2.

NSString

*str?=?@"/Users/yangiori/Library/Application Support/iPhone

Simulator/5.1/Applicati*****/8724956B-407E-4ACD-BBA6-95C7D033C33D/Documents/content/chapters/8";

NSString *temp2?=?[str substringFromIndex:[str length]-1];

NSLog(@"%@",temp2);

結果：8

5.從指定位置截取字符串

NSString * str =[NSString stringWithFormat:@"********************Documents/image%i.jpg",2];

NSRange range =?[str rangeOfString:@"Documents"];

NSString * result =?[str substringFromIndex:range.location];

NSLog(@"%@",result);

六、其他操作

1.擴展路徑

NSString *Path?=?@"~/NSData.txt";

NSString *absolutePath?=?[Path stringByExpandingTildeInPath];

NSLog(@"absolutePath:%@",absolutePath);

NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);

2.文件擴展名

NSString *Path?=?@"~/NSData.txt";

NSLog(@"Extension:%@",[Path pathExtension]);

NSMutableString

基本用法

1.給字符串分配容量

stringWithCapacity:

NSMutableString *String;

String =?[NSMutableString stringWithCapacity:40];

2.在已有字符串后面添加字符

appendString: and appendFormat: