OC Encapsulation Inheritance and instantiation

[Person new] has done three things:

1) Request Memory space

2) Initialize the instance

3) Return to the first address of the space

Instance variables are saved in the heap area

"Pointer (object name) saved in the stack area

Object methods are saved in the code area

The call method first finds the pointer to the heap area that P points to-isa and then finds the method of the code area that Isa points to

Object methods can only be called by objects, class methods can only be called by classes, and cannot be called as functions

The function belongs to the entire file, and the function declaration can be inside main or outside the main function, except @interface @end

Function:

1) So the functions are all parallel.

2) function has no affiliation

3) can be used when using the direct drop

4) You cannot access member variables in an object

@interface @end can not be nested

Member variables cannot be initialized at declaration time

Member variables and methods cannot be modified with static

[Person new] has done three things:

1) Request Memory space

2) Initialize the instance variable

3) Return to the first address of the space

Which area of the memory is requested for space:

New time to apply for space in the heap area of space

If the instance variable is a base type, it is initialized to 0 at this time.

If it is a string type, it is initialized to null

Where is the instance variable saved?

Heap Area

P (pointer variable name) stack area

Object methods are saved in the code area

Why [P run]; Can we call the method? How to invoke the

First find the space of P, then find the _isa, and then find the code space pointed to by _isa, and then find the method in the space

15) class Method:

Class method call does not require an instance

Invocation of class method [Class name class method name]

class method name and object method name can be the same

The benefit of class methods is that you do not need to create objects, access them directly through the class name, and do not need to create any space in the heap area

The class method does not allow access to the instance variable, you can pass a parameter

Instance methods can access instance variables

Object methods can call other methods of an object

Other methods of the class can be called in a class method, can be used with self, or a method method can be called with another class name

An object method can also be called in a class method, except by passing an object through a parameter or creating an object.

Class method cannot call itself (dead loop)

[[Car alloc] init] equals [car new]

Anonymous classes are used as method parameters:

Person *p = [[Person alloc] init]

[P Gohome:[car New];

16) Package:

Instance variables can only be accessed by object methods of the current class

Writing specification for Set methods:

1) The Set method must be an object method

2) The Set method must not have a return value

3) The Set method must start with set

4) set followed by the instance variable minus the underscore, and the first letter capitalized

5) The Set method must have parameters, and the type of the parameter and the instance variable are the same

6) There is no method overload in OC, the method in OC cannot have the same name

7) The variable defined by static can only be used in the current file

() Self:

Self refers to the object that invokes the current method

Self refers to the current class method

Person *p = [person new];

[P class]; Returns the current class

A variable with the same name as a global variable can be defined inside a function

Local variables temporarily mask the scope of global variables if they have the same name (can be distinguished by self)

18) Inheritance:

The private property of the base class is inherited, but cannot be used

In OC is single inheritance

Call the object method to find out if there is a method in this class, otherwise find the parent class

Supports multiple layers of inheritance

The variable default modifier is @protect

@private can only be used in object methods of the current class

Variables defined in. m are private variables

Methods that are not declared in. h are private methods

Private methods cannot inherit from a quilt class

NSLog ("%p", D); Print Object Address

NSLog ("%@", D); Print class name + object address

Prints Object D in%@ format, at which point the description method of the object is called, and if the description method is not overridden in the subclass, the parent class's

[D class]; Get the Dog class

Class methods cannot access instance variables

Do not use%@ and self in the description method will cause a dead loop

OC Encapsulation Inheritance and instantiation