Scott: /* Memory management */

2011-01-31T23:38:42Z

Memory management

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==Introduction==
Objective-C is a strict superset of C. It adds in the concept of messaging:
<source lang="objc">
[myArray insertObject:anObject atIndex:0];
</source>

==File management==
* <code>.h</code> is for header files, containing class, type, function, and constant declarations.
* <code>.m</code> is for source files, containing implementations.
* Use <code>#import</code> to access declarations from other files.

==Memory management==
If you create a variable of a non-builtin-type (not int or float), then you need to release it when you're done with it:
<source lang="objc">
[tempName release];
</source>
Call this within scope for a temporary variable, or in the class's <code>dealloc</code> method for an instance variable.

== Classes ==
Interface declaration in MyClass.h:
<source lang="objc">
#import "MySuperClass.h"

@interface MyClass : MySuperClass {
// instance variables
}
+classMethod1; // void return type
+(return_type)classMethod2; // takes no parameter
+(return_type)classMethod3:(param_type)paramName;
-(return_type)instanceMethod:(param_type)param1 :(param_type)param2;
-(return_type)instanceMethodWithNamedParameter:(param_type)param1 namedParameter:(param_type)param2;

@end
</source>

Another interface declaration in MyOtherClass.h:
<source lang="objc">
@interface MyOtherClass : NSObject
{
int count; // strongly typed
id data; // weakly typed - allows assignment of an arbitrary object
NSString* name; // strongly typed
}
- (id)initWithString:(NSString*)aName; // instance method
+ (MyOtherClass)createWithString:(NSString*)aName; // class method
@end
</source>

An implementation in MyOtherClass.m:
<source lang="objc">
@implementation MyOtherClass

- (id)initWithString:(NSString *)aName
{
if (self = [super init]) {
name = [aName copy];
}
return self;
}

+ (MyOtherClass *)createWithString: (NSString *)aName
{
return [[[self alloc] initWithString:aName] autorelease];
}
@end
</source>

== Class properties with getters and setters ==
In the .h file:
<source lang="objc">
@property BOOL flag;
@property (copy) NSString *nameObject; // Copy the object during assignment.
@property (readonly) UIView *rootView; // Declare only a getter method.
</source>
Generate the appropriate getters and setters in the .m file with synthesize:
<source lang="objc">
@synthesize flag, nameObject, rootView;
</source>

==Strings==
String literals must be preceded by an @ sign:
<source lang="objc">
NSString *myString = @"My String\n";
NSString *anotherString = [NSString stringWithFormat:@"%d %s", 1, @"String"];
</source>

==Resources==
http://www.devworld.apple.com/iphone/library/referencelibrary/GettingStarted/Learning_Objective-C_A_Primer/

http://www.devworld.apple.com/iphone/library/documentation/Cocoa/Conceptual/ObjectiveC/Introduction/introObjectiveC.html

http://www.devworld.apple.com/iphone/library/documentation/Cocoa/Conceptual/ObjectiveC/Articles/ocLanguageSummary.html

http://en.wikipedia.org/wiki/Objective-C

Objective C - Revision history

Scott: /* Memory management */