[OC Foundation框架

A. 不可变字符串

void stringCreate()
{
    //Don't need to release memory by this way
    NSString *str1 = @"String Sample";
   
    NSString *str2 = [[NSString alloc] init];
    str2 = @"String sample 2";
    [str2 release];
   
    NSString *str3 = [[NSString alloc] initWithString:@"String sample 3"];
    [str3 release];
    //Don't need to manage memory by static function
    str3 = [NSString stringWithString:@"A String"];
   
    NSString *str4 = [[NSString alloc] initWithUTF8String:"String sample4"];
    [str4 release];
    //No manual memory management, too
    str4 = [NSString stringWithUTF8String:"String 4"];
   
   
    NSString *str5 = [[NSString alloc] initWithFormat:@"My age is %i and height is %.2f", 19, 1.55];
    NSLog(@"String 5 is %@", str5);
    [str5 release];
}

 

B. 从文件读取字符串

void readFromFile()
{
    NSString *path = @"/Users/hellovoidworld/Study/Foundation/NSString/file.txt";
   
    //This function cannot read Chinese, is expired
//    NSString *str1 = [NSString stringWithContentsOfFile:path];
   
    NSError *error;
   
    NSString *str1 = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];
   
    if (error == nil)
    {
        NSLog(@"Read successfully, is %@", str1);
    }
    else
    {
        NSLog(@"Read fail, error is %@", error);
    }
}

 

C. 从URL读取

void readFromUrl()
{
    NSURL *url = [NSURL URLWithString:@"file:///Users/hellovoidworld/Study/Foundation/NSString/file.txt"];
    NSString *str2 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"Read url successfully, is %@", str2);
}