learnxinyminutes-docs/objective-c.html.markdown

367 lines
11 KiB
Markdown
Raw Normal View History

2013-08-13 12:32:20 +00:00
---
2013-08-13 12:38:39 +00:00
language: Objective-C
contributors:
- ["Eugene Yagrushkin", "www.about.me/yagrushkin"]
- ["Yannick Loriot", "https://github.com/YannickL"]
filename: LearnObjectiveC.m
2013-08-13 12:32:20 +00:00
---
2013-08-13 12:45:49 +00:00
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.
It is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language.
2013-08-13 12:32:20 +00:00
2013-08-13 17:30:44 +00:00
```cpp
2013-08-13 12:32:20 +00:00
// Single-line comments start with //
/*
Multi-line comments look like this.
*/
2013-08-13 12:56:09 +00:00
// Imports the Foundation headers with #import
#import <Foundation/Foundation.h>
2013-08-13 14:50:22 +00:00
#import "MyClass.h"
2013-08-13 12:56:09 +00:00
// Your program's entry point is a function called
// main with an integer return type.
int main (int argc, const char * argv[])
{
2013-08-13 14:04:20 +00:00
// Create an autorelease pool to manage the memory into the program
2013-08-13 12:56:09 +00:00
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
2013-08-13 13:25:47 +00:00
// Use NSLog to print lines to the console
2013-08-13 13:50:09 +00:00
NSLog(@"Hello World!"); // Print the string "Hello World!"
2013-08-13 12:56:09 +00:00
2013-08-13 14:04:20 +00:00
///////////////////////////////////////
// Types & Variables
///////////////////////////////////////
// Primitive declarations
2013-08-13 14:09:38 +00:00
int myPrimitive1 = 1;
long myPrimitive2 = 234554664565;
2013-08-13 14:04:20 +00:00
// Object declarations
// Put the * in front of the variable names for strongly-typed object declarations
2013-08-13 14:09:38 +00:00
MyClass *myObject1 = nil; // Strong typing
id myObject2 = nil; // Weak typing
2013-08-13 13:50:09 +00:00
// %@ is an object
2013-08-13 14:07:58 +00:00
// 'description' is a convention to display the value of the Objects
NSLog(@"%@ and %@", myObject1, [myObject2 description]); // Print "(null) and (null)"
2013-08-13 14:04:20 +00:00
// String
NSString *worldString = @"World";
NSLog(@"Hello %@!", worldString); // prints => "Hello World!"
// NSMutableString is a mutable version of the NSString object.
2013-12-22 16:37:02 +00:00
NSMutableString *mutableString = [NSMutableString stringWithString:@"Hello"];
[mutableString appendString:@" World!"];
NSLog(@"%@", mutableString); // prints => "Hello World!"
2013-08-13 13:50:09 +00:00
// Character literals
2013-08-13 13:52:11 +00:00
NSNumber *theLetterZNumber = @'Z';
2013-12-22 16:37:02 +00:00
char theLetterZ = [theLetterZNumber charValue]; // or 'Z'
2013-08-13 13:52:11 +00:00
NSLog(@"%c", theLetterZ);
2013-08-13 12:56:09 +00:00
2013-08-13 13:50:09 +00:00
// Integral literals
NSNumber *fortyTwoNumber = @42;
2013-12-22 16:37:02 +00:00
int fortyTwo = [fortyTwoNumber intValue]; // or 42
2013-08-13 13:50:09 +00:00
NSLog(@"%i", fortyTwo);
NSNumber *fortyTwoUnsignedNumber = @42U;
2013-12-22 16:37:02 +00:00
unsigned int fortyTwoUnsigned = [fortyTwoUnsignedNumber unsignedIntValue]; // or 42
2013-08-13 13:50:09 +00:00
NSLog(@"%u", fortyTwoUnsigned);
2013-08-13 14:04:20 +00:00
NSNumber *fortyTwoShortNumber = [NSNumber numberWithShort:42];
2013-12-22 16:37:02 +00:00
short fortyTwoShort = [fortyTwoShortNumber shortValue]; // or 42
2013-08-13 14:04:20 +00:00
NSLog(@"%hi", fortyTwoShort);
2013-12-22 16:37:02 +00:00
NSNumber *fortyTwoShortNumber = [NSNumber numberWithShort:41];
unsigned short fortyTwoUnsigned = [fortyTwoShortNumber unsignedShortValue]; // or 41
NSLog(@"%hu", fortyTwoUnsigned);
2013-08-13 14:04:20 +00:00
2013-08-13 13:50:09 +00:00
NSNumber *fortyTwoLongNumber = @42L;
2013-12-22 16:37:02 +00:00
long fortyTwoLong = [fortyTwoLongNumber longValue]; // or 42
2013-08-13 13:50:09 +00:00
NSLog(@"%li", fortyTwoLong);
2013-12-22 16:37:02 +00:00
NSNumber *fortyTwoLongNumber = @53L;
unsigned long fiftyThreeUnsigned = [fortyTwoLongNumber unsignedLongValue]; // or 53
NSLog(@"%lu", fiftyThreeUnsigned);
2013-08-13 13:50:09 +00:00
// Floating point literals
NSNumber *piFloatNumber = @3.141592654F;
2013-12-22 16:37:02 +00:00
float piFloat = [piFloatNumber floatValue]; // or 3.141592654f
NSLog(@"%f", piFloat); // prints => 3.141592654
NSLog(@"%5.2f", piFloat); // prints => " 3.14"
2013-08-13 13:50:09 +00:00
NSNumber *piDoubleNumber = @3.1415926535;
2013-12-22 16:37:02 +00:00
double piDouble = [piDoubleNumber doubleValue]; // or 3.1415926535
2013-08-13 13:50:09 +00:00
NSLog(@"%f", piDouble);
2013-12-22 16:37:02 +00:00
NSLog(@"%4.2f", piDouble); // prints => "3.14"
// NSDecimalNumber is a fixed-point class that's more precise then float or double
2013-12-22 16:37:02 +00:00
NSDecimalNumber *oneDecNum = [NSDecimalNumber decimalNumberWithString:@"10.99"];
NSDecimalNumber *twoDecNum = [NSDecimalNumber decimalNumberWithString:@"5.002"];
// NSDecimalNumber isn't able to use standard +, -, *, / operators so it provides its own:
[oneDecNum decimalNumberByAdding:twoDecNum];
2013-12-22 16:37:02 +00:00
[oneDecNum decimalNumberBySubtracting:twoDecNum];
[oneDecNum decimalNumberByMultiplyingBy:twoDecNum];
[oneDecNum decimalNumberByDividingBy:twoDecNum];
NSLog(@"%@", oneDecNum); // prints => 10.99 as NSDecimalNumber is immutable.
2013-08-13 12:32:20 +00:00
2013-08-13 13:25:47 +00:00
// BOOL literals
2013-08-13 13:50:09 +00:00
NSNumber *yesNumber = @YES;
NSNumber *noNumber = @NO;
2013-12-22 16:37:02 +00:00
// or
BOOL yesBool = YES;
BOOL noBool = NO;
NSLog(@"%i", yesBool); // prints => 1
2013-08-13 13:50:09 +00:00
// Array object
NSArray *anArray = @[@1, @2, @3, @4];
NSNumber *thirdNumber = anArray[2];
2013-08-17 22:06:23 +00:00
NSLog(@"Third number = %@", thirdNumber); // Print "Third number = 3"
2013-12-22 16:37:02 +00:00
// NSMutableArray is mutable version of NSArray allowing to change items in array
// and extend or shrink array object. Convenient, but not as efficient as NSArray.
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:2];
[mutableArray addObject:@"Hello"];
[mutableArray addObject:@"World"];
[mutableArray removeObjectAtIndex:0];
NSLog(@"%@", [mutableArray objectAtIndex:0]); // prints => "World"
2013-08-13 13:50:09 +00:00
// Dictionary object
NSDictionary *aDictionary = @{ @"key1" : @"value1", @"key2" : @"value2" };
NSObject *valueObject = aDictionary[@"A Key"];
NSLog(@"Object = %@", valueObject); // Print "Object = (null)"
// NSMutableDictionary also available as mutable dictionary object.
2013-08-13 12:32:20 +00:00
2013-12-22 16:37:02 +00:00
// Set object
NSSet *set = [NSSet setWithObjects:@"Hello", @"Hello", @"World", nil];
NSLog(@"%@", set); // prints => {(Hello, World)} (may be in different order)
// NSMutableSet also available as mutable set object.
2013-12-22 16:37:02 +00:00
2013-08-13 14:04:20 +00:00
///////////////////////////////////////
// Operators
///////////////////////////////////////
2013-08-13 14:22:40 +00:00
// The operators works like in the C language
// For example:
2013-08-13 14:32:16 +00:00
2 + 5; // => 7
4.2f + 5.1f; // => 9.3f
2013-08-13 14:22:40 +00:00
3 == 2; // => 0 (NO)
3 != 2; // => 1 (YES)
1 && 1; // => 1 (Logical and)
0 || 1; // => 1 (Logical or)
~0x0F; // => 0xF0 (bitwise negation)
0x0F & 0xF0; // => 0x00 (bitwise AND)
0x01 << 1; // => 0x02 (bitwise left shift (by 1))
///////////////////////////////////////
// Control Structures
///////////////////////////////////////
// If-Else statement
if (NO)
{
NSLog(@"I am never run");
} else if (0)
{
NSLog(@"I am also never run");
} else
{
NSLog(@"I print");
}
// Switch statement
2013-08-13 14:32:16 +00:00
switch (2)
{
2013-08-13 14:22:40 +00:00
case 0:
{
NSLog(@"I am never run");
} break;
case 1:
{
NSLog(@"I am also never run");
} break;
default:
{
NSLog(@"I print");
} break;
}
2013-08-13 14:32:16 +00:00
// While loops statements
2013-08-13 14:22:40 +00:00
int ii = 0;
while (ii < 4)
{
NSLog(@"%d,", ii++); // ii++ increments ii in-place, after using its value.
2013-08-13 14:32:16 +00:00
} // => prints "0,"
2013-08-13 14:34:12 +00:00
// "1,"
// "2,"
// "3,"
2013-08-13 14:22:40 +00:00
2013-08-13 14:32:16 +00:00
// For loops statements
2013-08-13 14:22:40 +00:00
int jj;
for (jj=0; jj < 4; jj++)
{
NSLog(@"%d,", jj);
2013-08-13 14:32:16 +00:00
} // => prints "0,"
2013-08-13 14:34:12 +00:00
// "1,"
// "2,"
// "3,"
2013-08-13 14:22:40 +00:00
2013-08-13 14:32:16 +00:00
// Foreach statements
2013-08-13 14:22:40 +00:00
NSArray *values = @[@0, @1, @2, @3];
for (NSNumber *value in values)
{
NSLog(@"%@,", value);
2013-08-13 14:32:16 +00:00
} // => prints "0,"
2013-08-13 14:34:12 +00:00
// "1,"
// "2,"
// "3,"
2013-08-13 14:04:20 +00:00
// Object for loop statement. Can be used with any Objective-C object type.
for (id item in values) {
NSLog(@"%@,", item);
} // => prints "0,"
// "1,"
// "2,"
// "3,"
2013-08-13 14:32:16 +00:00
// Try-Catch-Finally statements
@try
{
// Your statements here
2013-08-13 17:30:44 +00:00
@throw [NSException exceptionWithName:@"FileNotFoundException"
reason:@"File Not Found on System" userInfo:nil];
2013-08-13 14:32:16 +00:00
} @catch (NSException * e)
{
NSLog(@"Exception: %@", e);
} @finally
{
NSLog(@"Finally");
} // => prints "Exception: File Not Found on System"
2013-08-13 14:34:12 +00:00
// "Finally"
2013-08-13 14:32:16 +00:00
2013-08-13 14:49:23 +00:00
///////////////////////////////////////
// Objects
///////////////////////////////////////
// Create an object instance by allocating memory and initializing it.
// An object is not fully functional until both steps have been completed.
MyClass *myObject = [[MyClass alloc] init];
2013-08-13 17:30:44 +00:00
// The Objective-C model of object-oriented programming is based on message
// passing to object instances.
2013-08-13 14:49:23 +00:00
// In Objective-C one does not simply call a method; one sends a message.
2013-08-13 17:30:44 +00:00
[myObject instanceMethodWithParameter:@"Steve Jobs"];
2013-08-13 14:49:23 +00:00
2013-08-13 13:25:47 +00:00
// Clean up the memory you used into your program
[pool drain];
2013-08-13 14:04:20 +00:00
// End the program
2013-08-13 13:25:47 +00:00
return 0;
}
2013-08-13 12:32:20 +00:00
2013-08-13 13:25:47 +00:00
///////////////////////////////////////
// Classes And Functions
///////////////////////////////////////
2013-08-13 12:32:20 +00:00
2013-08-13 14:50:22 +00:00
// Declare your class in a header(MyClass.h) file:
2013-08-13 14:46:16 +00:00
// Class Declaration Syntax:
2013-08-13 14:58:13 +00:00
// @interface ClassName : ParentClassName <ImplementedProtocols>
2013-08-13 14:46:16 +00:00
// {
// Member variable declarations;
// }
// -/+ (type) Method declarations;
// @end
@interface MyClass : NSObject <MyProtocol>
2013-08-13 13:25:47 +00:00
{
2013-08-13 14:46:16 +00:00
int count;
id data;
NSString *name;
2013-08-13 12:32:20 +00:00
}
2013-08-13 14:58:13 +00:00
// Convenience notation to auto generate public getter and setter
@property int count;
@property (copy) NSString *name; // Copy the object during assignment.
@property (readonly) id data; // Declare only a getter method.
2013-12-21 23:37:19 +00:00
// To access public variable in implementation file, use '_' followed by variable name:
_count = 5;
2013-12-21 23:37:19 +00:00
NSLog(@"%d", _count); // prints => 5
// To access public variable outside implementation file, @property generates setter method
// automatically. Method name is 'set' followed by @property variable name:
[objInitVar setCount:10]; // objInitVar = random object instance @property resides in.
2013-12-21 23:37:19 +00:00
NSLog(@"%@", [objInitVar count]); // prints => 10
2013-08-13 14:46:16 +00:00
// Methods
+/- (return type)methodSignature:(Parameter Type *)parameterName;
2013-08-13 12:32:20 +00:00
2013-08-13 14:46:16 +00:00
// + for class method
2013-08-13 13:25:47 +00:00
+ (NSString *)classMethod;
2013-08-13 12:32:20 +00:00
2013-08-13 14:46:16 +00:00
// - for instance method
2013-09-04 11:56:58 +00:00
- (NSString *)instanceMethodWithParameter:(NSString *)string;
2013-08-13 14:46:16 +00:00
- (NSNumber *)methodAParameterAsString:(NSString*)string andAParameterAsNumber:(NSNumber *)number;
2013-08-13 17:30:44 +00:00
2013-08-13 12:32:20 +00:00
@end
2013-08-13 14:50:22 +00:00
// Implement the methods in an implementation (MyClass.m) file:
2013-08-13 12:32:20 +00:00
@implementation MyClass
2013-08-13 12:32:20 +00:00
2013-08-13 14:58:13 +00:00
// Call when the object is releasing
- (void)dealloc
{
}
2013-08-13 14:46:16 +00:00
// Constructors are a way of creating classes
// This is a default constructor which is called when the object is creating
2013-08-13 14:46:16 +00:00
- (id)init
{
if ((self = [super init]))
{
self.count = 1;
}
return self;
}
2013-08-13 13:25:47 +00:00
+ (NSString *)classMethod
{
2013-08-13 14:46:16 +00:00
return [[self alloc] init];
2013-08-13 12:32:20 +00:00
}
2013-09-04 11:56:58 +00:00
- (NSString *)instanceMethodWithParameter:(NSString *)string
2013-08-13 12:32:20 +00:00
{
2013-08-13 13:25:47 +00:00
return @"New string";
2013-08-13 12:32:20 +00:00
}
2013-08-13 13:25:47 +00:00
- (NSNumber *)methodAParameterAsString:(NSString*)string andAParameterAsNumber:(NSNumber *)number
2013-08-13 12:32:20 +00:00
{
2013-08-13 13:25:47 +00:00
return @42;
2013-08-13 12:32:20 +00:00
}
2013-08-13 13:25:47 +00:00
2013-08-13 14:58:13 +00:00
// Methods declared into MyProtocol
- (void)myProtocolMethod
{
// statements
}
2013-08-13 12:32:20 +00:00
@end
2013-08-13 14:58:13 +00:00
/*
* A protocol declares methods that can be implemented by any class.
* Protocols are not classes themselves. They simply define an interface
* that other objects are responsible for implementing.
2013-08-13 17:30:44 +00:00
*/
2013-08-13 14:58:13 +00:00
@protocol MyProtocol
- (void)myProtocolMethod;
@end
2013-08-13 12:32:20 +00:00
```
## Further Reading
[Wikipedia Objective-C](http://en.wikipedia.org/wiki/Objective-C)
2013-08-13 12:45:49 +00:00
[Learning Objective-C](http://developer.apple.com/library/ios/referencelibrary/GettingStarted/Learning_Objective-C_A_Primer/)
2013-08-13 12:32:20 +00:00
[iOS For High School Students: Getting Started](http://www.raywenderlich.com/5600/ios-for-high-school-students-getting-started)