NSString. Write to file. Read from file.

This small program below show the simplest way to create an ASCII text file, write a string into it and read the string from the file:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) 
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSString* lastLine    = @"Beauty is truth, truth beauty";
    NSString* fileName    = @"GrecianUrn.txt";
    NSString* homeDir    = NSHomeDirectory();
    
    NSString* fullPath = [homeDir stringByAppendingPathComponent:fileName];
    
    NSError* error = nil;
    [lastLine writeToFile:fullPath atomically:NO encoding:NSASCIIStringEncoding error:&error];
    
    NSStringEncoding encoding;
    NSString* contents = [NSString stringWithContentsOfFile:fullPath usedEncoding:&encoding
                          error:&error];
    
    NSLog(@"Content of '%@': %@", fileName, contents);
    
    [pool drain];
    return 0;
}

Objective-C. Forwarding Messages.

Forwarding messages. It's an absolutely new feature for me in Object-Oriented Programming. I found this thing working in Objective-C (thanks to the book - on the left).

#import <Foundation/Foundation.h>

@interface Cat : NSObject
- (void) meow;
@end

@interface Dog : NSObject
- (void) woof;
@end

@implementation Cat

- (void) meow
{
    NSLog( @"%@: Meow", [self className] );
}

@end

@implementation Dog

- (void) woof
{
    NSLog( @"%@: woof", [self className] );
}

- (NSMethodSignature*) methodSignatureForSelector:(SEL)selector
{
    NSString* name = NSStringFromSelector( selector );
    NSLog( @"-[%@: methodSignatureForSelector: %@]", [self className], name );
    
    if ([Cat instancesRespondToSelector: selector])
        return [Cat instanceMethodSignatureForSelector: selector];
    
    return [super methodSignatureForSelector: selector];
}

- (void) forwardInvocation:(NSInvocation *)anInvocation
{
    NSString* name = NSStringFromSelector( anInvocation.selector );
    NSLog( @"-[%@: forwardInvocation: %@]", [self className], name );
    
    id theCat = [[Cat alloc] init];
    NSLog( @"Forwarding '%@' to %@", name, theCat );
    [anInvocation invokeWithTarget: theCat];
    [theCat release];
}

@end

int main() 
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
    id dog = [[Dog alloc] init];
    [dog woof];
    [dog meow];
    [dog release];

    [pool drain];
    return 0;
}

And here is the output:

Running…

Dog: woof

-[Dog: methodSignatureForSelector: meow]

-[Dog: forwardInvocation: meow]

Forwarding 'meow' to

Cat: Meow

64-bit Objective-C

On 64-bit you can use properties to generate both accessor methods and the instance variable itself. This code compiles and works on Snow Leopard:

#import <Foundation/Foundation.h>

@interface Test : NSObject
@property (retain) NSString *name;
@end

@implementation Test
@synthesize name;
@end

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    Test *test = [[Test alloc] init];
    [test setName: @"TheName"];
    NSLog(@"Name is %@\n", [test name]);
    [pool drain];
    return 0;
}

Here is the console:

Program loaded.

run

[Switching to process 2963]

Running…

2010-06-12 00:42:30.308 Test64[2963:a0f] Name is TheName

Debugger stopped.

Program exited with status value:0.

Cocoa and Objective-C Up and Running.

I've read already many book about Objective-C and didn't think that I can find something new in this one. I was wrong. It's really a great book.
For example:
[object method];
[object methodWithInput: inputValue];
Objective-C is a dynamic language, so technically you are not calling a method directly when you use this syntax; you are actually sending a message. Calling a method is basically issuing an order, whereas sending a message is more like making a request.

AppleScript. Automator.

Two nice articles on Mac.AppStorm:
1. Automator: The Ultimate Automation Assistant
2. Advanced AppleScript Techniques

Objective-C classes at runtime

Great article:
Obj-C Optimization: Allocation Basics & Foundation

AppleScript. Hello, World!

You can find AppleScript Editor in the folder Utilities of Applications:

Type "Hello":

Press Compile and then Run - see "Hello" in the result window:

Let's "complicate" the script. Type:

display alert "Hello"

Press Compile and Run. You see a simple alert with one Ok button on the screen:

Let's make an application from it. In the File menu select "Save as". You will see this save dialog:

Select "Application" in the File Format combo box. Set a name, for example Hello. Set a path - I set the desktop:

Now on the desktop I see my Hello application. When I click on it, I see my alert:

In the end of this post I'd like to show a less useless and a bit funny example. You can use AppleScript editor as a calculator. Simply type something you need to calculate, compile and run it:

Of course you can arrange it as a script:

display alert 45 + 16 * 2 / 3

This book below contains a nice section about AppleScript: