学步园

//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];