Objective-C concepts to be remembered

1. Definition class: In. H files,

@ Interface Class Name: parent class name

{

Member variables;

}

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.