Fernando Rodriguez Romero

Cajón de nerd

¿Congreso de Internet o Chiringo de Intenné?

El tal "congreso de internet" al que he ido esta  mañana está siendo una enorme decepción, gracias a la ausencia absoluta de organización por parte de la empresa que lo perpetra. Es la segunda vez que acudo a dicho evento, y mucho me temo que será la última.

Cuando hice la inscripción, recuerdo que recibí un email de confirmación indicándome la fecha del congreso…con un año de error (2009). Mal empezamos… A pesar de esto, mi sorpresa ha sido mayúscula al llegar al "Congreso de Internet" y ver que ¡no había internet!  En pleno 2010 (y no 2009 como creían los "organizadores"), montan un congreso con las siguientes características:
  • En una sala de reunión de un hotel en la que es imposible ver las diapositivas de los ponentes.
  • Micrófonos que fallan continuamente.
  • No hay azafatas que lleven los micrófonos nuevos al ponente ni a los asistentes que hacen preguntas: se tiene que buscar la vida el ponente.
  • El principal ponente, o al menos el más esperado por los asistentes, ya no va a ir.
  • ¿Se me olvidaba decir que NO HAY INTERNET?
Las ponencias no están siendo de momento para tirar cohetes, con la excepción de la de Javier Ortiz sobre SEO, que me ha parecido muy buena. Este señor, después estar peleando con los micrófonos (sin ningún tipo de asistencia por parte de los "organizadores"), ha tenido que ver la imagen profesional de su ponencia dañada por la falta absoluta de medios (¿quién me da unos prismáticos para ver las diapositivas?).

Los doscientos y pico que estaríamos allí habremos malgastado nuestro dinero, pero al menos nuestra imagen no se ha visto asociada a ese desorden absoluto.

Esto NO es serio, y desde luego no pienso volver a acudir a ningún evento que organice esta gente. 

Recuerdo que el primero al que acudí (en el Palacio de Congresos y que se llamaba "Congreso de Webmasters"), a parte de ponencias interesantes, tenía una infraestructura adecuada para el evento. Algún tiempo después se organizó en el mismo lugar otro evento similar llamado "Congreso de Internet", organizado por un tío de Toledo, cuyo nombre desgraciadamente no recuerdo. Ese sí fue muy interesante y la organización impecable. Una lástima que no se haya repetido. 

En comparación, este último "Congreso de webmasters" rebautizado como "Congreso de Internet" es un desastre sin paliativos. Ya que querían cambiarle el nombre (vaya Ud a saber por qué), habría sido más adecuado ponerle "Chiringo de Intenné". Sin intenné, claro está….

Learn Objective-C with "Programming in Objective-C" by Stephen G. Kochan

Sample Source Code

Unlike smalltalk, the full source code is not available. The  implementation files are delivered compiled by Apple and only the header's are in source form.  There are however, several OpenStep forks that are open sourced:

  1. mySTEP: http://www.quantum-step.com/wiki.php?page=mySTEP&referer=mySTEP
  2. Cocotron: an open source version of Cocoa. 
See also : http://stackoverflow.com/questions/419362/cocoa-objective-c-can-i-somehow-see-the-implementation-files

Other interesting source code is the provided by the OMNI folks: http://www.omnigroup.com/company/developer

Introduction

ObjetiveC is case sensitive

#import is similar to #include, but prevents repeated inclusion

@ precedes any ObjetiveC specific keyword

all message sending goes inside []

As you can see from the comments in Program 3.2, the program is logically divided into three sections:

@interface 
@implementation
program

The @interface section describes the class, its data components, and its methods, whereas the @implementation section contains the actual code that implements these methods. Finally, the program section contains the program code to carry out the in- tended purpose of the program.

Instance variables can be accessed from any instance method, but from nowhere else, including class methods.

The method new is a shortcut for alloc and init:
Fraction *myFraction = [[Fraction alloc] init];
Fraction *myFraction = [Fraction new];

Data Types

int
double
char

int     integerVar = 100; 
float floatingVar = 331.79; 
double doubleVar = 8.44e+11; 
char     charVar = ‘W’;

long, long long, signed and unsigned qualifier

long and "long long" increase the size of the type up to 64 bits.

long long int maxAllowedStorage;

unsigned int counter;
Restricting the use of an integer variable to the exclusive storage of positive integers extends the accuracy of the integer variable.

The id data type is used to store an object of any type. In a sense, it is a generic object
type. It implies a pointer, so there's no need to type *id. 

For example, this line declares number to be a variable of type id: 
id number;

Methods can be declared to return values of type id, like so:

 -(id) newObject: (int) type;

Type Cast

The type cast operator is often used to coerce an object that is a generic id type into an object of a particular class. 

For example, the following lines convert the value of the id variable myNumber to a Fraction object:

id myNumber; 
Fraction *myFraction;

… 

myFraction = (Fraction *) myNumber;

The result of the conversion is assigned to the Fraction variable myFraction.

_Bool

_Bool, for working with Boolean (that is, 0 or 1) values. 

Objective-C programmers tend to use the BOOL data type instead of _Bool for working with Boolean values in their programs.This “data type” is actually not a data type unto it- self, but is another name for the char data type.This is done with the language’s special typedef keyword.

BOOL isPrime;

isPrime = YES;
or
isPrime = NO;

otherwise,

_Bool isPrime;
isPrime = true;
isPrime = false;

Apple's ObjetiveC's frameworks use BOOL.

Looping Constructs

int n, triangularNum;


for( n = 1 ; n <= 200; n++){
triangularNum += n;
}

---------------
int n, triangularNum;


n = 1;
while (n<= 200) {
triangularNum += n;


n++;
}

----------------

int n, triangularNum;


n = 1;
do {
triangularNum += n;
n++;
} while (n <= 200);



Branching

if ( expression 1 )
      program statement 1
else if ( expression 2 )
      program statement 2
else program statement 3

switch ( operator ) { 
     case ‘+’:
          [deskCalc add: value2];
          break; 
     case ‘-’:
          [deskCalc subtract: value2];
          break; 
     case ‘*’:
          [deskCalc multiply: value2];
          break; 
     case ‘/’:
          [deskCalc divide: value2];
          break; 
     default:
          NSLog (@”Unknown operator.”); 
          break;
}

Class Files

As in VB6, each class goes in it's own file:
Class.h -> @interface
Class.m -> @implementation

Automatic (synthesized) Accessor Methods

ObjetiveC 2.0 can automagically create accessor methods for an instance variable x called "x" and "setX". These methods are thread-safe.

In the implementation file ".h" mark the the variables with the @property directive and then apply the @synthesize directive to the same variables in the implementation module:

//
//  Fraction.h
//  FractionTest
//
//  Created by Fernando Rodríguez Romero on 10/7/10.
//  Copyright 2010 AGBO Business Architecture, SL. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Fraction : NSObject {

int  numerator;
int denominator;
}

@property int numerator, denominator; (¡OJO! hay que repetir el tipo, en este caso un int)

-(void) print;
-(void) setNumerator: (int) n;
-(void) setDenominator: (int) d;
-(int) numerator;
-(int) denominator;
-(double) convertToNum;

@end

//
//  Fraction.m
//  FractionTest
//
//  Created by Fernando Rodríguez Romero on 10/7/10.
//  Copyright 2010 AGBO Business Architecture, SL. All rights reserved.
//

#import "Fraction.h"

@implementation Fraction

@synthesize numerator, denominator;

-(void) print {
     NSLog(@"%i/%i", numerator, denominator);
}

-(double) convertToNum {
     if (denominator != 0) {
          return (double) numerator / denominator;
     }else {
          return1.0;
     }
}

@end

Dot syntactic sugar

[myFraction setNumerator: 1];
[myFraction denominator];

Here’s an equivalent way to write the same two lines:

myFraction.numerator = 1; 
myFraction.denominator;

Messages with multiple arguments

Similar to Smalltalk:

-(void) setTo: (int) n over: (int) d;

-(void) setTo:(int)n over:(int)d {
     numerator = n;
     denominator = d;

}

Methods with no argument names

When creating the name for a method, the argument names are actually optional. For example, you can declare a method like this:

-(int) set: (int) n: (int) d;

This method is named set::, and the two colons mean the method takes two arguments, even though they’re not all named.

To invoke the set:: method, you use the colons as argument delimiters, as shown here:

 [aFraction set: 1 : 3];

This is a bad thing.

Methods that take another object as a parameter

-(void) add: (Fraction *) aFraction;

Notice the asterisk: all references are actually pointers to objects.

¡OJO!

As the parameter is a pointer to an object, if the callee saves it and the caller later modifies it, it will change the state of the object!

All instances should OWN any object passed as a parameter in a method.  You must therefore make a local copy of the parameter (are there methods for deep or shallow copy on NSObject?). You must also release this instance explicitly by overrinding the dealloc method of super.

Overriding the dealloc method and the keyword super

the release method only decreases the reference count of the object. If the refcount is zero, it deallocates the memory by sending the message dealloc.

You only overrride the method dealloc. Since dealloc returns an id, the overriding method should be:

-(id) dealloc {
  if (ownedObject) {
               [ownedObject release];
     }


     return [superdealloc];
}

Static keyword

The static modifier has the same meaning as in vb6.

Self keyword

Same as in Smalltalk.

Methods that return objects

If a method returns an object, it is paramount that the caller releases the returned object!

-(Fraction *) add: (Fraction *) f

Maybe that's why some messages in the book return void instead of self (as in Smalltalk).

@class directive

The @class directive is a more efficient alternative to including a header file when we only need to mention a class, without ever using any of its methods. Not worth using it.

Constructors "a la Smalltalk"

Build them with class methods, just like in Smalltalk. However, it's common for their names to begin with "init".

//
//  Complex.h
//  FractionTest
//
//  Created by Fernando Rodríguez Romero on 10/8/10.
//  Copyright 2010 AGBO Business Architecture, SL. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Complex : NSObject {
doublereal;
doubleimaginary;

}

@property double real, imaginary;

-(void) print;
-(void) setReal: (double) a andImaginary: (double) b;
-(Complex *) add: (Complex *) f;