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authorAdam Bard <github@adambard.com>2014-01-23 08:39:44 -0800
committerAdam Bard <github@adambard.com>2014-01-23 08:39:44 -0800
commit0524f0479f80943c8ab757af75e1dc2e3456f5ac (patch)
treed40013e5f24be32ed7c4ea7a8a53402ea7e3c901 /objective-c.html.markdown
parentec3ea2b0902d579decb4bf0a02fdb672453ea5e0 (diff)
parent39cbd8141e57cf626f310b65ae97058b5387ed1d (diff)
Merge pull request #490 from YannickL/master
Minor changes for the objective-c file
Diffstat (limited to 'objective-c.html.markdown')
-rw-r--r--objective-c.html.markdown138
1 files changed, 72 insertions, 66 deletions
diff --git a/objective-c.html.markdown b/objective-c.html.markdown
index f2787649..453a42a5 100644
--- a/objective-c.html.markdown
+++ b/objective-c.html.markdown
@@ -12,19 +12,25 @@ filename: 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.
-```cpp
+```objective-c
// Single-line comments start with //
/*
-Multi-line comments look like this.
+Multi-line comments look like this
*/
// Imports the Foundation headers with #import
+// Use <> to import global files (in general frameworks)
+// Use "" to import local files (from project)
#import <Foundation/Foundation.h>
#import "MyClass.h"
+// If you enable modules for iOS >= 7.0 or OS X >= 10.9 projects in
+// Xcode 5 you can import frameworks like that:
+@import Foundation;
+
// Your program's entry point is a function called
-// main with an integer return type.
+// main with an integer return type
int main (int argc, const char * argv[])
{
// Create an autorelease pool to manage the memory into the program
@@ -54,7 +60,7 @@ int main (int argc, const char * argv[])
// String
NSString *worldString = @"World";
NSLog(@"Hello %@!", worldString); // prints => "Hello World!"
- // NSMutableString is a mutable version of the NSString object.
+ // NSMutableString is a mutable version of the NSString object
NSMutableString *mutableString = [NSMutableString stringWithString:@"Hello"];
[mutableString appendString:@" World!"];
NSLog(@"%@", mutableString); // prints => "Hello World!"
@@ -108,7 +114,7 @@ int main (int argc, const char * argv[])
[oneDecNum decimalNumberBySubtracting:twoDecNum];
[oneDecNum decimalNumberByMultiplyingBy:twoDecNum];
[oneDecNum decimalNumberByDividingBy:twoDecNum];
- NSLog(@"%@", oneDecNum); // prints => 10.99 as NSDecimalNumber is immutable.
+ NSLog(@"%@", oneDecNum); // prints => 10.99 as NSDecimalNumber is immutable
// BOOL literals
NSNumber *yesNumber = @YES;
@@ -119,12 +125,12 @@ int main (int argc, const char * argv[])
NSLog(@"%i", yesBool); // prints => 1
// Array object
- // May contain different data types, but must be an Objective-C object.
+ // May contain different data types, but must be an Objective-C 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.
+ // and extend or shrink array object. Convenient, but not as efficient as NSArray
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:2];
[mutableArray addObject:@"Hello"];
[mutableArray addObject:@"World"];
@@ -135,7 +141,7 @@ int main (int argc, const char * argv[])
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 also available as a mutable dictionary object
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithCapacity:2];
[mutableDictionary setObject:@"value1" forKey:@"key1"];
[mutableDictionary setObject:@"value2" forKey:@"key2"];
@@ -144,7 +150,7 @@ int main (int argc, const char * argv[])
// 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 also available as a mutable set object
NSMutableSet *mutableSet = [NSMutableSet setWithCapacity:2];
[mutableSet addObject:@"Hello"];
[mutableSet addObject:@"Hello"];
@@ -203,7 +209,7 @@ int main (int argc, const char * argv[])
int ii = 0;
while (ii < 4)
{
- NSLog(@"%d,", ii++); // ii++ increments ii in-place, after using its value.
+ NSLog(@"%d,", ii++); // ii++ increments ii in-place, after using its value
} // => prints "0,"
// "1,"
// "2,"
@@ -229,7 +235,7 @@ int main (int argc, const char * argv[])
// "2,"
// "3,"
- // Object for loop statement. Can be used with any Objective-C object type.
+ // Object for loop statement. Can be used with any Objective-C object type
for (id item in values) {
NSLog(@"%@,", item);
} // => prints "0,"
@@ -256,19 +262,19 @@ int main (int argc, const char * argv[])
// Objects
///////////////////////////////////////
- // Create an object instance by allocating memory and initializing it.
- // An object is not fully functional until both steps have been completed.
+ // 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.
+ // 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 of @autoreleasepool.
+ // End of @autoreleasepool
}
// End the program
@@ -285,22 +291,22 @@ int main (int argc, const char * argv[])
// {
// type name; <= variable declarations;
// }
-// @property type name; <= property declarations.
-// -/+ (type) Method declarations; <= Method declarations.
+// @property type name; <= property declarations
+// -/+ (type) Method declarations; <= Method declarations
// @end
@interface MyClass : NSObject <MyProtocol> // NSObject is Objective-C's base object class.
{
- // Instance variable declarations (can exist in either interface or implementation file).
+ // 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).
+ @private id data; // Private access (More convenient to declare in implementation file)
NSString *name;
}
-// Convenient notation for public access variables to auto generate a setter method.
-// By default, setter method name is 'set' followed by @property variable name.
+// Convenient notation for public access variables to auto generate a setter method
+// By default, setter method name is 'set' followed by @property variable name
@property int propInt; // Setter method name = 'setPropInt'
-@property (copy) id copyId; // (copy) => Copy the object during assignment.
-// (readonly) => Cannot set value outside @interface.
-@property (readonly) NSString *roString; // Use @synthesize in @implementation to create accessor.
+@property (copy) id copyId; // (copy) => Copy the object during assignment
+// (readonly) => Cannot set value outside @interface
+@property (readonly) NSString *roString; // Use @synthesize in @implementation to create accessor
// You can customize the getter and setter names instead of using default 'set' name:
@property (getter=lengthGet, setter=lengthSet:) int length;
@@ -317,14 +323,14 @@ int main (int argc, const char * argv[])
// Constructor methods with arguments:
- (id)initWithDistance:(int)defaultDistance;
-// Objective-C method names are very descriptive. Always name methods according to their arguments.
+// Objective-C method names are very descriptive. Always name methods according to their arguments
-@end // States the end of the interface.
+@end // States the end of the interface
// To access public variables from the implementation file, @property generates a setter method
// automatically. Method name is 'set' followed by @property variable name:
-MyClass *myClass = [[MyClass alloc] init]; // create MyClass object instance.
+MyClass *myClass = [[MyClass alloc] init]; // create MyClass object instance
[myClass setCount:10];
NSLog(@"%d", [myClass count]); // prints => 10
// Or using the custom getter and setter method defined in @interface:
@@ -339,39 +345,39 @@ NSString *classMethodString = [MyClass classMethod];
MyClass *classFromName = [MyClass myClassFromName:@"Hello"];
// Call instance methods:
-MyClass *myClass = [[MyClass alloc] init]; // Create MyClass object instance.
+MyClass *myClass = [[MyClass alloc] init]; // Create MyClass object instance
NSString *stringFromInstanceMethod = [myClass instanceMethodWithParameter:@"Hello"];
-// Selectors.
+// Selectors
// Way to dynamically represent methods. Used to call methods of a class, pass methods
// through functions to tell other classes they should call it, and to save methods
-// as a variable.
-// SEL is the data type. @selector() returns a selector from method name provided.
+// as a variable
+// SEL is the data type. @selector() returns a selector from method name provided
// methodAParameterAsString:andAParameterAsNumber: is method name for method in MyClass
SEL selectorVar = @selector(methodAParameterAsString:andAParameterAsNumber:);
-if ([myClass respondsToSelector:selectorVar]) { // Checks if class contains method.
- // Must put all method arguments into one object to send to performSelector function.
+if ([myClass respondsToSelector:selectorVar]) { // Checks if class contains method
+ // Must put all method arguments into one object to send to performSelector function
NSArray *arguments = [NSArray arrayWithObjects:@"Hello", @4, nil];
- [myClass performSelector:selectorVar withObject:arguments]; // Calls the method.
+ [myClass performSelector:selectorVar withObject:arguments]; // Calls the method
} else {
- // NSStringFromSelector() returns a NSString of the method name of a given selector.
+ // NSStringFromSelector() returns a NSString of the method name of a given selector
NSLog(@"MyClass does not have method: %@", NSStringFromSelector(selectedVar));
}
// Implement the methods in an implementation (MyClass.m) file:
@implementation MyClass {
- long distance; // Private access instance variable.
+ long distance; // Private access instance variable
NSNumber height;
}
// To access a public variable from the interface file, use '_' followed by variable name:
-_count = 5; // References "int count" from MyClass interface.
+_count = 5; // References "int count" from MyClass interface
// Access variables defined in implementation file:
-distance = 18; // References "long distance" from MyClass implementation.
+distance = 18; // References "long distance" from MyClass implementation
// To use @property variable in implementation, use @synthesize to create accessor variable:
-@synthesize roString = _roString; // _roString available now in @implementation.
+@synthesize roString = _roString; // _roString available now in @implementation
-// Called before calling any class methods or instantiating any objects.
+// Called before calling any class methods or instantiating any objects
+ (void)initialize
{
if (self == [MyClass class]) {
@@ -379,20 +385,20 @@ distance = 18; // References "long distance" from MyClass implementation.
}
}
-// Counterpart to initialize method. Called when an object's reference count is zero.
+// Counterpart to initialize method. Called when an object's reference count is zero
- (void)dealloc
{
[height release]; // If not using ARC, make sure to release class variable objects
- [super dealloc]; // and call parent class dealloc.
+ [super dealloc]; // and call parent class dealloc
}
-// Constructors are a way of creating instances of a class.
-// This is a default constructor which is called when the object is initialized.
+// Constructors are a way of creating instances of a class
+// This is a default constructor which is called when the object is initialized.
- (id)init
{
- if ((self = [super init])) // 'super' used to access methods from parent class.
+ if ((self = [super init])) // 'super' used to access methods from parent class
{
- self.count = 1; // 'self' used for object to call itself.
+ self.count = 1; // 'self' used for object to call itself
}
return self;
}
@@ -424,11 +430,11 @@ distance = 18; // References "long distance" from MyClass implementation.
return @42;
}
-// To create a private method, create the method in the @implementation but not in the @interface.
+// To create a private method, create the method in the @implementation but not in the @interface
- (NSNumber *)secretPrivateMethod {
return @72;
}
-[self secretPrivateMethod]; // Calls private method.
+[self secretPrivateMethod]; // Calls private method
// Methods declared into MyProtocol
- (void)myProtocolMethod
@@ -436,7 +442,7 @@ distance = 18; // References "long distance" from MyClass implementation.
// statements
}
-@end // States the end of the implementation.
+@end // States the end of the implementation
/*
* A protocol declares methods that can be implemented by any class.
@@ -466,34 +472,34 @@ With all object interactions, follow the pattern of:
(1) create the object, (2) use the object, (3) then free the object from memory.
*/
-MyClass *classVar = [MyClass alloc]; // 'alloc' sets classVar's reference count to one. Returns pointer to object.
-[classVar release]; // Decrements classVar's reference count.
-// 'retain' claims ownership of existing object instance and increments reference count. Returns pointer to object.
-MyClass *newVar = [classVar retain]; // If classVar is released, object is still in memory because newVar is owner.
-[classVar autorelease]; // Removes ownership of object at end of @autoreleasepool block. Returns pointer to object.
+MyClass *classVar = [MyClass alloc]; // 'alloc' sets classVar's reference count to one. Returns pointer to object
+[classVar release]; // Decrements classVar's reference count
+// 'retain' claims ownership of existing object instance and increments reference count. Returns pointer to object
+MyClass *newVar = [classVar retain]; // If classVar is released, object is still in memory because newVar is owner
+[classVar autorelease]; // Removes ownership of object at end of @autoreleasepool block. Returns pointer to object
-// @property can use 'retain' and 'assign' as well for small convenient definitions.
-@property (retain) MyClass *instance; // Release old value and retain a new one (strong reference).
-@property (assign) NSSet *set; // Pointer to new value without retaining/releasing old (weak reference).
+// @property can use 'retain' and 'assign' as well for small convenient definitions
+@property (retain) MyClass *instance; // Release old value and retain a new one (strong reference)
+@property (assign) NSSet *set; // Pointer to new value without retaining/releasing old (weak reference)
// Automatic Reference Counting (ARC)
// Because memory management can be a pain, Xcode 4.2 and iOS 4 introduced Automatic Reference Counting (ARC).
// ARC is a compiler feature that inserts retain, release, and autorelease automatically for you, so when using ARC,
-// you must not use retain, relase, or autorelease.
+// you must not use retain, relase, or autorelease
MyClass *arcMyClass = [[MyClass alloc] init];
// ... code using arcMyClass
// Without ARC, you will need to call: [arcMyClass release] after you're done using arcMyClass. But with ARC,
-// there is no need. It will insert this release statement for you.
+// there is no need. It will insert this release statement for you
-// As for the 'assign' and 'retain' @property attributes, with ARC you use 'weak' and 'strong'.
+// As for the 'assign' and 'retain' @property attributes, with ARC you use 'weak' and 'strong'
@property (weak) MyClass *weakVar; // 'weak' does not take ownership of object. If original instance's reference count
-// is set to zero, weakVar will automatically receive value of nil to avoid application crashing.
-@property (strong) MyClass *strongVar; // 'strong' takes ownership of object. Ensures object will stay in memory to use.
+// is set to zero, weakVar will automatically receive value of nil to avoid application crashing
+@property (strong) MyClass *strongVar; // 'strong' takes ownership of object. Ensures object will stay in memory to use
// For regular variables (not @property declared variables), use the following:
-__strong NSString *strongString; // Default. Variable is retained in memory until it leaves it's scope.
-__weak NSSet *weakSet; // Weak reference to existing object. When existing object is released, weakSet is set to nil.
-__unsafe_unretained NSArray *unsafeArray; // Like __weak, but unsafeArray not set to nil when existing object is released.
+__strong NSString *strongString; // Default. Variable is retained in memory until it leaves it's scope
+__weak NSSet *weakSet; // Weak reference to existing object. When existing object is released, weakSet is set to nil
+__unsafe_unretained NSArray *unsafeArray; // Like __weak, but unsafeArray not set to nil when existing object is released
```
## Further Reading