NSString 用法1

http://blog.sina.com.cn/s/blog_8c87ba3b0100tgxs.html 

//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!";
    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);

    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)

//如何判断字符串为空

NSString *urlString = [urlInput stringValue];

if (!urlString) {

NSLog( @”NO INPUT.” );

} else {

if ([urlString length] == 0 ) {

NSLog( @”NO INPUT.” );

} else {

}
}
}

Convert NSString to int
1 NSString *aNumberString = @"123";
2 int i = [aNumberString intValue];

 

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use @"abc" to mean NSString
ex: NSString *str = @"Hello";

use content of file to create NSString
ex: NSString *str = [NSString stringWithContentsOfFile:@"/path/to/file"]

use c characters to create NSString
ex: char *cStr="hello";
NSString *str = [NSString stringWithCString: cStr]

get length of NSString
ex: unsigned int strLen = [str length]

append on NSString to another
ex: NSString *str = @"Hello";
NSString *str2 = [str stringByAppendingString: @"abc"]

append a format:
ex: NSString *str3 = [str2 stringByAppendingFormat: @"%d", 2003]

search for subString:
ex: NSRange loc = [str rangeOfString:@"The"]

what is NSRange:
typedef struct _NSRange{
unsigned int location;
unsigned int length;
}NSRange;

breaking a string into components:
ex: NSArray *fields = [str componentsSeperatedByString:@"abc"];

create NSMutableString from NSString:
ex: NSString *str = @"hello";
NSMutableString *ms = [NSMutableString stringWithString: str];