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| language | contributors | filename | ||||||
|---|---|---|---|---|---|---|---|---|
| Objective-C |
|
LearnObjectiveC.m |
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.
// Single-line comments start with //
/*
Multi-line comments look like this.
*/
// Imports the Foundation headers with #import
#import <Foundation/Foundation.h>
#import "MyClass.h"
// Your program's entry point is a function called
// main with an integer return type.
int main (int argc, const char * argv[])
{
// Create an autorelease pool to manage the memory into the program
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
// Use NSLog to print lines to the console
NSLog(@"Hello World!"); // Print the string "Hello World!"
///////////////////////////////////////
// Types & Variables
///////////////////////////////////////
// Primitive declarations
int myPrimitive1 = 1;
long myPrimitive2 = 234554664565;
// Object declarations
// Put the * in front of the variable names for strongly-typed object declarations
MyClass *myObject1 = nil; // Strong typing
id myObject2 = nil; // Weak typing
// %@ is an object
// 'description' is a convention to display the value of the Objects
NSLog(@"%@ and %@", myObject1, [myObject2 description]); // Print "(null) and (null)"
// String
NSString *worldString = @"World";
NSLog(@"Hello %@!", worldString); // prints => "Hello World!"
// NSMutableString is a mutable version of the NSString object.
NSMutableString *mutableString = [NSMutableString stringWithString:@"Hello"];
[mutableString appendString:@" World!"];
NSLog(@"%@", mutableString); // prints => "Hello World!"
// Character literals
NSNumber *theLetterZNumber = @'Z';
char theLetterZ = [theLetterZNumber charValue]; // or 'Z'
NSLog(@"%c", theLetterZ);
// Integral literals
NSNumber *fortyTwoNumber = @42;
int fortyTwo = [fortyTwoNumber intValue]; // or 42
NSLog(@"%i", fortyTwo);
NSNumber *fortyTwoUnsignedNumber = @42U;
unsigned int fortyTwoUnsigned = [fortyTwoUnsignedNumber unsignedIntValue]; // or 42
NSLog(@"%u", fortyTwoUnsigned);
NSNumber *fortyTwoShortNumber = [NSNumber numberWithShort:42];
short fortyTwoShort = [fortyTwoShortNumber shortValue]; // or 42
NSLog(@"%hi", fortyTwoShort);
NSNumber *fortyTwoShortNumber = [NSNumber numberWithShort:41];
unsigned short fortyTwoUnsigned = [fortyTwoShortNumber unsignedShortValue]; // or 41
NSLog(@"%hu", fortyTwoUnsigned);
NSNumber *fortyTwoLongNumber = @42L;
long fortyTwoLong = [fortyTwoLongNumber longValue]; // or 42
NSLog(@"%li", fortyTwoLong);
NSNumber *fortyTwoLongNumber = @53L;
unsigned long fiftyThreeUnsigned = [fortyTwoLongNumber unsignedLongValue]; // or 53
NSLog(@"%lu", fiftyThreeUnsigned);
// Floating point literals
NSNumber *piFloatNumber = @3.141592654F;
float piFloat = [piFloatNumber floatValue]; // or 3.141592654f
NSLog(@"%f", piFloat); // prints => 3.141592654
NSLog(@"%5.2f", piFloat); // prints => " 3.14"
NSNumber *piDoubleNumber = @3.1415926535;
double piDouble = [piDoubleNumber doubleValue]; // or 3.1415926535
NSLog(@"%f", piDouble);
NSLog(@"%4.2f", piDouble); // prints => "3.14"
// NSDecimalNumber is a fixed-point class that's more precise then float or double
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];
[oneDecNum decimalNumberBySubtracting:twoDecNum];
[oneDecNum decimalNumberByMultiplyingBy:twoDecNum];
[oneDecNum decimalNumberByDividingBy:twoDecNum];
NSLog(@"%@", oneDecNum); // prints => 10.99 as NSDecimalNumber is immutable.
// BOOL literals
NSNumber *yesNumber = @YES;
NSNumber *noNumber = @NO;
// or
BOOL yesBool = YES;
BOOL noBool = NO;
NSLog(@"%i", yesBool); // prints => 1
// Array object
NSArray *anArray = @[@1, @2, @3, @4];
NSNumber *thirdNumber = anArray[2];
NSLog(@"Third number = %@", thirdNumber); // Print "Third number = 3"
// 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"
// Dictionary object
NSDictionary *aDictionary = @{ @"key1" : @"value1", @"key2" : @"value2" };
NSObject *valueObject = aDictionary[@"A Key"];
NSLog(@"Object = %@", valueObject); // Print "Object = (null)"
// NSMutableDictionary also available as a mutable dictionary object.
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithCapacity:2];
[mutableDictionary setObject:@"value1" forKey:@"key1"];
[mutableDictionary setObject:@"value2" forKey:@"key2"];
[mutableDictionary removeObjectForKey:@"key1"];
// Set object
NSSet *set = [NSSet setWithObjects:@"Hello", @"Hello", @"World", nil];
NSLog(@"%@", set); // prints => {(Hello, World)} (may be in different order)
// NSMutableSet also available as a mutable set object.
NSMutableSet *mutableSet = [NSMutableSet setWithCapacity:2];
[mutableSet addObject:@"Hello"];
[mutableSet addObject:@"Hello"];
NSLog(@"%@", mutableSet); // prints => {(Hello)}
// Set object
NSSet *set = [NSSet setWithObjects:@"Hello", @"Hello", @"World", nil];
NSLog(@"%@", set); // prints => {(Hello, World)}
///////////////////////////////////////
// Operators
///////////////////////////////////////
// The operators works like in the C language
// For example:
2 + 5; // => 7
4.2f + 5.1f; // => 9.3f
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
switch (2)
{
case 0:
{
NSLog(@"I am never run");
} break;
case 1:
{
NSLog(@"I am also never run");
} break;
default:
{
NSLog(@"I print");
} break;
}
// While loops statements
int ii = 0;
while (ii < 4)
{
NSLog(@"%d,", ii++); // ii++ increments ii in-place, after using its value.
} // => prints "0,"
// "1,"
// "2,"
// "3,"
// For loops statements
int jj;
for (jj=0; jj < 4; jj++)
{
NSLog(@"%d,", jj);
} // => prints "0,"
// "1,"
// "2,"
// "3,"
// Foreach statements
NSArray *values = @[@0, @1, @2, @3];
for (NSNumber *value in values)
{
NSLog(@"%@,", value);
} // => prints "0,"
// "1,"
// "2,"
// "3,"
// 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,"
// Try-Catch-Finally statements
@try
{
// Your statements here
@throw [NSException exceptionWithName:@"FileNotFoundException"
reason:@"File Not Found on System" userInfo:nil];
} @catch (NSException * e)
{
NSLog(@"Exception: %@", e);
} @finally
{
NSLog(@"Finally");
} // => prints "Exception: File Not Found on System"
// "Finally"
///////////////////////////////////////
// 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];
// The Objective-C model of object-oriented programming is based on message
// passing to object instances.
// In Objective-C one does not simply call a method; one sends a message.
[myObject instanceMethodWithParameter:@"Steve Jobs"];
// Clean up the memory you used into your program
[pool drain];
// End the program
return 0;
}
///////////////////////////////////////
// Classes And Functions
///////////////////////////////////////
// Declare your class in a header(MyClass.h) file:
// Class Declaration Syntax:
// @interface ClassName : ParentClassName <ImplementedProtocols>
// {
// Member variable declarations;
// }
// -/+ (type) Method declarations;
// @end
@interface MyClass : NSObject <MyProtocol>
{
// Instance variable declarations (can exist in either interface or implementation file)
int count; // Protected access by default.
@private id data; // Private access. (More convenient to declare in implementation file)
NSString *name;
}
// Convenient notation to auto generate public access getter and setter
@property int count;
@property (copy) NSString *name; // Copy the object during assignment.
@property (readonly) id data; // Declare only a getter method.
// To access public variable in implementation file, use '_' followed by variable name:
_count = 5;
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:
MyClass *myClass = [[MyClass alloc] init]; // create MyClass object instance.
[myClass setCount:10];
NSLog(@"%@", [myClass count]); // prints => 10
// You can customize the getter and setter names instead of using default 'set' name:
@property (getter=countGet, setter=countSet:) int count;
[myClass countSet:32];
NSLog(@"%i", [myClass countGet]); // prints => 32
// For convenience, you may use dot notation to set object instance variables:
myClass.count = 45;
NSLog(@"%i", myClass.count); // prints => 45
// Methods
+/- (return type)methodSignature:(Parameter Type *)parameterName;
// + for class method
+ (NSString *)classMethod;
// - for instance method
- (NSString *)instanceMethodWithParameter:(NSString *)string;
- (NSNumber *)methodAParameterAsString:(NSString*)string andAParameterAsNumber:(NSNumber *)number;
@end
// Implement the methods in an implementation (MyClass.m) file:
@implementation MyClass {
long count; // Private access instance variable.
}
// Call when the object is releasing
- (void)dealloc
{
}
// Constructors are a way of creating classes
// This is a default constructor which is called when the object is creating
- (id)init
{
if ((self = [super init]))
{
self.count = 1;
}
return self;
}
+ (NSString *)classMethod
{
return [[self alloc] init];
}
- (NSString *)instanceMethodWithParameter:(NSString *)string
{
return @"New string";
}
- (NSNumber *)methodAParameterAsString:(NSString*)string andAParameterAsNumber:(NSNumber *)number
{
return @42;
}
// Methods declared into MyProtocol
- (void)myProtocolMethod
{
// statements
}
@end
/*
* 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.
*/
@protocol MyProtocol
- (void)myProtocolMethod;
@end