iPhone objective-c字串類NSString的使用

開發過程中，我們會遇到很多關於字串的操作，它是一個常用的資料類型，下面對它的用法進行了匯總：

   

    //1、建立常量字串。

    NSString *astring = @"This is a
String!";

    //2、建立Null 字元串，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建立字串:initWithCString方法

    char *Cstring = "This is a
String!";

    NSString *astring = [[NSString alloc]
initWithCString:Cstring];

    NSLog(@"astring:%@",astring);

    [astring release];

    //5、建立格式化字串:預留位置（由一個%加一個字元組成）

    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、建立臨時字串

    NSString *astring;

    astring = [NSString stringWithCString:"This
is a temporary string"];

    NSLog(@"astring:%@",astring);

    NSString *path = @"astring.text";

    NSString *astring = [[NSString alloc]
initWithContentsOfFile:path];

    NSLog(@"astring:%@",astring);

    [astring release];

    NSString *astring = [[NSString alloc]
initWithString:@"This is a String!"];

    NSLog(@"astring:%@",astring);

    NSString *path =
@"astring.text";    

    [astring writeToFile: path atomically:
YES];

    [astring
release];    

  
        

    //用C比較: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為真)

    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為真)

//不考慮大 小寫比較字串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為
真)

 

//如何判斷字串為空白

NSString *urlString = [urlInput stringValue];

if
(!urlString) {





NSLog(
@”NO INPUT.”
);






}
else
{



if
([urlString length] ==
0
) {





NSLog(
@”NO INPUT.”
);





}
else
{





}






}


}