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122 lines
3.0 KiB
Markdown
122 lines
3.0 KiB
Markdown
---
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language: Objective-C
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contributors:
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- ["Eugene Yagrushkin", "www.about.me/yagrushkin"]
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- ["Yannick Loriot", "https://github.com/YannickL"]
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filename: LearnObjectiveC.m
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---
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Objective-C is the main programming language used by Apple for the OS X and iOS operating systems and their respective frameworks, Cocoa and Cocoa Touch.
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It is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language.
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```Objective-C
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// Single-line comments start with //
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/*
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Multi-line comments look like this.
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*/
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// Imports the Foundation headers with #import
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#import <Foundation/Foundation.h>
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// Your program's entry point is a function called
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// main with an integer return type.
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int main (int argc, const char * argv[])
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{
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// Create an autorelease pool to manage the memory into your program
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NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
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// Print "Hello World!" to the console
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NSLog(@"Hello World!");
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// Clean up the memory you used into your program
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[pool drain];
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// End your program
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return 0;
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}
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// all the primitive variable types are the same as in C
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// char, int, long, double, float
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// Simple, common classes
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// number
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NSNumber *firstNumber = @1;
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NSNumber *secondNumber = @23.0;
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NSNumber *boolNumber = @YES;
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// string
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NSString *aString = @"some string";
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// array
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NSArray *array = @[ @1, @2];
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// dictionary
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NSDictionay *dictionary = @{ @"aKey" : @"aValue", @"aKey2" : @"aValue2" };
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// Import headers with #import
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#import <UIKit/UIKit.h>
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#import "SomeAppDelegate.h"
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##Coding classes
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// Declare your class in a header(.h) file:
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@interface UserObject : NSObject{
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// instance variables
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}
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// Class method
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+ (NSString*) ClassMethod;
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// Instance method
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- (NSString*) instanceMethodWithParmeter:(NSString*)string;
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@end
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// Add class methods in an implementation (.m) file:
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@implementation UserObject
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+ (NSString*) ClassMethod{
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return @"SomeString";
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}
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- (NSString*) instanceMethodWithParmeter:(NSString*)string;
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{
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return @"New string";
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}
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- (NSString*) otherMethodWithString:(NSString*)string;
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{
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return [NSString stringWithString:string];
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}
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@end
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// Create an object instance by allocating memory and initializing it. An object is not fully functional until both steps have been completed.
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UserObject *someObject = [[UserObject alloc] init];
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##Calling Methods
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// The Objective-C model of object-oriented programming is based on message passing to object instances.
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// In Objective-C one does not simply call a method; one sends a message.
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[someObject instanceMethodWithParmeter:@"Steve Jobs"];
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##Nested Messages
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// nested messages look like this:
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[someObject instanceMethodWithParmeter:[someObject otherMethodWithString:@"Jony Ive"]];
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```
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## Further Reading
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[Wikipedia Objective-C](http://en.wikipedia.org/wiki/Objective-C)
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[Learning Objective-C](http://developer.apple.com/library/ios/referencelibrary/GettingStarted/Learning_Objective-C_A_Primer/)
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[iOS For High School Students: Getting Started](http://www.raywenderlich.com/5600/ios-for-high-school-students-getting-started)
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