In-depth analysis of Objective-C small concepts

AboutObjective-CA small concept is the content to be introduced in this article, mainly to understandObjective-CTo learn the details. Let's take a look at the details.

1. Definition class: In the. h file,

 
 

  
  
@ Interface Class Name: parent class name
  
  
{
  
  
Member variables;
  
  
}
 
 

1. member functions;

 
 

  
  
@end； 
 
 

In the. m file, @ implementation class name member function definition;

 
 

  
  
@end； 
 
 

2. member function definition:-(Return Value Type) function name: (parameter type) parameter ,...

 
 

  
  
-(void) setColor:(NSString*)newColor  
  
  
 {  
  
  
    Color=newColor;  
  
  
 }      
  
  
 -(void) setNumber:(int)newNumber  
  
  
 {  
  
  
    Number=newNumber;  
  
  
 } 
 
 

3. instantiation class:

 
 

  
  
myCar=[Car new];  
  
  
[myCar setColor:red];  
  
  
[myCar setNumber:Num]; 
 
 

4. @ class command:

When you want to use another defined class in a class, use @ class. If you want to use the method, # import this class.

5. Memory Management:

The iphone operating system does not support garbage collection.

Generally, alloc + init is used to create an object, and new is also available;

Alloc, copy, retain, release, autorelease;

6. Foundation framework:

 
 

  
  
@ Import <Foundation/Foundation. h>
  
  
NSString class, NSMutableString class;
  
  
NSArray class, NSMutableArray class;
  
  
NSDictionary class, NSMutableDictionary class;
 
 

7. accessors:

When declaring a class variable, you can make it an attribute. @ Property int Number;

In the. m file, add @ synthesize Number to automatically generate the setter and getter methods;

In this way, you can use the dot operator to access the member variable, car. Number = 27;

8. Create an object:

 
 

  
  
Id object name = [class name alloc];
  
  
[Object Name init];
  
  
Boat * boat = [[Boat allco] init];
  
  
Boat * boat = [[Boat alloc] initWithNum: 123
  
  
Color: @ "red"];
 
 

In general, write as follows during init:

 
 

  
  
-Init
  
  
{
  
  
If (self = [super init]) {
  
  
// Initialization
  
  
Return self;
  
  
}
 
 

When parameters exist,

 
 

  
  
-(id) initWithNum:(int) Num  
  
  
      Color:(NSString*) Color; 
 
 

9. variable scope:

If there is no scope restriction, the default value is protected;

10. @ try exception handling:

 
 

  
  
@try{}  
  
  
@catch(NSException *exception){NSLog(@"Catch exception name :%@; reason:%@;",  
  
  
                              [exception name],[exception reason]);}  
  
  
@finally{} 
 
 

11. Categories and protocols:

Sometimes you need to add some methods to a defined class without rewriting the class. You can use a category ).

If you have defined a Circle class, in the CircleCal. h file,

 
 

  
  
@import "Circle.h"  
  
  
@interface Circle(CircleCal)  
  
  
-(float) AreaCal;  
  
  
-(float) LenCal;  
  
  
@end; 
 
 

In the CircleCal. m file,

 
 

  
  
#import "CircleCal.h"  
  
  
@implementation Circle(CircleCal)  
  
  
-(float) AreaCal{}  
  
  
-(float) LenCal{}  
  
  
@end; 
 
 

In this case, the new defined function can be called in the main function;

Ps: the category cannot add instance variables to the class. The category can overwrite the methods in the class to be extended, but avoid them as much as possible. When a category is used to expand a class, it will also affect the subclass of this class.

The Protocol is a list of methods. It declares a series of methods without implementation. The Protocol is not the class itself, there is no parent class, and member variables cannot be defined.

 
 

  
  
@protocol Calculating  
  
  
-(void) CalculateArea;  
  
  
@end;  
  
  
@interface Rectangle:NSObject <Calculating>{} 
 
 

When defining a member function in Rectangle, you must also define the method in Calculating to call it.

@ Protocol has two modifiers: @ optional and @ required,

The method modified by @ optional can be disabled in the class using this protocol, but the method modified by @ required must be implemented. The default value is @ required.

Summary: I have thoroughly analyzed the content about the Objective-C small concept. I hope this article will help you!