about objects · objective-c basics morning session b objects, classes, and methods messages and...

About Objects

Introduction to Objective-CSECTION 1

Developer–oriented training.

www.AboutObjects.com

Friday, October 9, 2009

About Objects

Reston, VA — Cupertino, CA

Training

ANSI C

Objective-C

iPhone SDK

Cocoa/Cocoa touch

360iDev Denver

Thanks to Conference organizers

Tom Ortega

John Wilker

And everyone else who helped: Great job!

About Objects delighted to take part

Look forward to continued sponsorship of future events.

How about Washington, D.C. for future conference?

About The Instructors

Jonathan Lehr

President, About Objects

Developer, author, speaker

Objective-C developer/trainer since 1991

Developer–oriented training.

About You

Are you familiar with other dev technologies?

Kinds of iPhone features you like to learn to develop?

Have you been trying to learn some things on your own?

Topics, Morning Day 1

Given the one-day format, we'll limit the scope.

Morning Session A

Using Xcode

Objective-C Basics

Morning Session B

Objects, Classes, and Methods

Messages and the Objective-C runtime system

Memory Management

Declared Properties

Topics, Afternoon, Day 1

Afternoon Session A

Overview of UIKit and Interface Builder

Applications, Windows, Views

ViewControllers and UIControls

Afternoon Session B

TableViews, Delegates, and DataSources

IB Outlets and Actions

Multiple Nib Files

Customizing UI Components

Overview

What is Objective-C?

ANSI C + Object-Oriented extensions

Combines the best of static and dynamic languages

GNU C compiler compiles both C and Objective-C code

Apple donated Objective-C to the GNU open source project

What are Cocoa and Cocoa touch?

Cocoa is Mac UI layer

Cocoa touch is Cocoa on the iPhone

Each contains two Objective-C frameworks

Foundation (collections, value types, utility classes, etc.)

UIKit (iPhone) or AppKit (Mac)

Developer Tools

XCode IDE

Run (Simulator, device)

Debug (gdb)

Source code management (SCM)

Documentation

All major platforms

Mac OS X

iPhone OS

Features

Syntax-aware code editor with completion, etc.

Automates builds

Context-sensitive documentation browser

Interface Builder

Visual GUI design tool

Doesn't generate code

Works with ‘Freeze-dried’ objects

Archived (serialized) in .nib files

Dynamically loaded

Objects deserialized at load time

Instruments

Profiling

Performance Monitoring

Garage-Band 'multi-track' interface

Profiling

Performance Monitoring

Garage-Band 'multi-track' interface

History of Objective-C

Smalltalk

Earliest OO language (circa 1972) — Allen Kay, Xerox PARC

Objective-C

Developed in early eights to address Smalltalk performance (Brad Cox)

Licensed in '85 by NeXT Computer

Steve Jobs, Avie Tevanian

Used in UI layer, dev tools, and apps.

User Interface, Circa 1996

Apple/NeXT Merger, '96

Objective-C at Apple

Apple acquires NeXT in 1996 for modern OS to replace Mac OS 9

Apple then ported OpenStep to Motorola's PowerPC architecture

Added Quartz 2D rendering engine to replace Adobe Display PostScript

Ported Mac Toolbox APIs (Carbon)

New OS released 2001 as OS X 10.0

iPhone OS

Port of Mac OS X to mobile platform

First release (2.0b2) March, 2008

Objective-C Basics

Message Syntax

Square brackets for message expressions

myString.toString()

Objective-C

[myString description]

Method Arguments

Arguments are delimited by colons

person.setFirstName("Fred");

Objective-C

[person setFirstName:@"Fred"];

Constants

Constant string object different from constant string

"Hello"

Objective-C

@"Hello" // String object"Hello" // C string

Object Data Types

Objective-C objects are dynamically allocated structs

Variable types are therefore pointers to struct defined by class

Employee emp = new Employee();

Objective-C

Employee *emp = [[Employee alloc] init];

Obj-C also provides generic object type, id

id emp2 = [[Employee alloc] init];

Constructors vs. Creation Methods

No constructors; creation methods are just methods

Ordinary return statements provide more flexibility

Calls to super can occur anywhere within a method

Inheritance is straight-forward

Memory allocation and initialization are separate steps

Employee emp = new Employee();

Objective-C

Employee *emp = [[Employee alloc] init];

Prefix vs. Package Path

Obj-C language doesn't provide namespaces

Frameworks and libraries use prefixes by convention to avoid collisions

java.lang.String s = new String("hello");

Objective-C

NSString *s = [[NSString alloc] initWithString:"hi"];

Classes

Two separate files

Class declared in .h file

Methods implemented in .m file

Compiler directives

@interface ... @end

@implementation ... @end

Curly braces

Instance variable section inside curly braces

Methods defined outside curly braces

Anatomy of a Class Declaration

@interface Person : NSObject { int _age; NSString * _firstName;}

compiler directive

class we're declaring class it inherits from

name of instance variabledata type

Class Declaration: Methods

@interface Person : NSObject { ... // Instance variables go here}

// Method declarations start here...

- (int)age;

- (void) setAge: (int)anAge;

return type

method name

arg type

arg name

#import <Foundation/Foundation.h>

// Following line declares the Person class as a subclass of NSObject

@interface Person : NSObject { // Instance Variables. Note: Underscore prefix is conventional but not required. int _age; NSString *_firstName;}

// Methods. Note: Getter methods are not prefixed with 'get'.

- (int)age; // Returns person's age.- (void)setAge:(int anAge); // Sets person's age to anAge.

- (NSString *)firstName; // Returns person's first name.- (void)setFirstName:(NSString *)aName; // Set person's first name to aName.

Class Declaration

#import "Person.h"

@implementation Person

- (int)age{ return _age;}

- (void)setAge:(int age){ _age = age;}

- (NSString *)firstName{ return firstName;}

- (void)setFirstName:(NSString *)firstName{ _firstName = firstName; // Note: This code omits some memory management details...}

Class Implementation

Method Prototypes

Methods declared in .h, implemented in .m

Data types enclosed in parens

Instance methods prefixed with -

Class methods prefixed with +

// Method declarations- (id)init;+ (id)alloc;

No Method Overloading

Runtime system looks up methods by name rather than signature

Makes introspection simpler and more efficient

manager.addEmployee(emp);manager.addEmployee(emp, "Developer");

Objective-C

[manager addEmployee:emp];[manager addEmployee:emp withTitle:@"Developer"];

Multi-Argument Methods

Method names can be composed of multiple sections

Each section ends with a colon that delimits the next arg

public void addEmployee(Employee emp, String title)

Objective-C

- (void)addEmployee:(Employee *)emp withTitle:(NSString *)title

Name of method is addEmployee:withTitle:

Args are emp and title

Visibility Modifiers

Compiler directives

@private

@protected

@public

No visibility modifiers for methods

Methods made 'private' by omitting declarations from .h file.

To emphasize 'privacy', prefix method name with underscore.

@interface Person : NSObject{

// Visibility modifier. Applies to all ivars that follow.@private // Private instance variables. NSString *_firstName; NSNumber *_salary;

@protected // Protected instance variables. int _age; }

// Instance methods....

Using Visibility Modifiers

Writing a Program

World's Shortest Obj-C Program

What makes this Objective-C?

It's in a file named main.m

String constant prefixed with @ (which makes it a string object in Obj-C)

More than just an Objective-C program; it's a Foundation tool!

Imports Foundation.h

Calls Foundation's NSLog function (a C function)

#import <Foundation/Foundation.h>

int main(){ NSLog(@"Hello, World!");}

Working with Xcode

Setting Preferences

Creating a Project

Adding Groups

Adding Files

Building and Fixing Compilation Errors

Running

Preferences: IDE Layout

Select All-In-One. If drop down disabled, close any open projects !rst.

Preferences: Building

Set to Always.

Preferences: Debugging

Select Show Console & Debugger.

Preferences: Fonts & Colors

➊ Click Duplicate.

➋ Click on a row and choose Select All from the menu.

➌ Type ⌘T to bring up Font Panel and click to select font size.

Preferences: Indentation

➋ Select Always.

➊ Check Syntax-aware indenting.

Preferences: SCM

➋ Fill in repository info.

➊ To set up SCM (not needed for this course), click + to add repositories.

➌ If using SSH, go to SSH tab to supply identities.

Add New Group

➋ Select New Group...

➊ Right-click project name.

Add New File

➋ Select New File...

➊ Right-click Group name.

➌ Select a !le template.

Start Editing

Class declaration code generated from template.

.h and .m !les added automatically.

Inline error messages.

Click Build and Run when ready to build.

Compiler output.

Run/Debug

Console.

Code editor. Debugger pane.

1. Create a project named Hello World

2. Build and Run

3. Change the ‘Hello World!’ message to ‘Farewell World!’ and build and run again

Resources

Example Code:

http://www.aboutobjects.com/tutorials.html

Documentation:

Objective-C: http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/Introduction/introObjectiveC.html

iPhone: http://developer.apple.com/iphone/library/navigation/index.html

Courses:

http://www.aboutobjects.com/training/courses.html

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