NSString赋值方法

　　//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!";
    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];