[IOS development] Object, ios development object

[IOS development] Object, ios development object

.

I. Class Definition

Class definition needs to be implemented in two parts:

--Interface Section: Define the member variables and methods of the class. The methods are abstract and defined in the header file;

--Implementation: Introduce the header file of the interface to implement the abstract method;

1. Interface Definition

(1) Interface Definition Format

Interface Definition Format:

@ Interface className:SuperClassName

{

Type _ variableName;

......

}

-(Type) methodName: type parameterName;

@ End

--Interface Definition start ID: @ Interface indicates that the interface is defined;

--End ID of the Interface Definition: @ End indicates that the interface definition has ended;

--Interface Name Definition: The class name followed by @ interface;

--Parent Interface: If there is a parent class, write it after: After the interface name;

--Member variable definition: Define member variables in {} after @ interface;

--Member Method: Define the member variable in {} and then define the member method;

(2) member variable definition

.

Note: The Return Value Type and parameter type in the member method must be included in () to distinguish it from the C-language method;

.

Member variables:

--Definition Format: Type member variable name, such as int _ age;

--Define location: Defined in braces in the next line of @ interface, and the variable to the right is defined in braces;

--Available type: Basic type, construction type, various pointer types;

--Naming rules: Generally, we recommend that you start with "_" for member variables and name them in the hump format;

(3) member Method

Member Methods:

--Member method format:Method type identifier (Return Value Type) method name:(Parameter type) parameter name method signature Keyword: (parameter type) parameter name;

--Method identifier: "+" Indicates the class method, and "-" indicates the instance method;

--Method signature keyword: A method name, a parameter label, and a colon;

--Parameter label: Object-C Convention. Apart from the first parameter, a parameter label is created for each parameter;

Meaning of method Signature:

--"Method": Indicates that the method has no parameters;

--"Method :": Indicates that the method has a form parameter;

--"Method: param :": Indicates that the method has two parameters;

(4) sample code of some interfaces

Example:

/*************************************** * *********************************> File Name: student. h> Author: octopus> Mail: octopus_truth.163.com> Created Time: 12/14 19:51:16, 2014 Class interface Example ******************************** **************************************** /# import <Foundation/Foundation. h> @ interface Student: NSObject {/** member variables are defined in brackets of the interface declaration. * Note that the member variables start with "_" */NSString * _ name before they begin; int _ age;}/** defines setData: setAge: Method *-indicates that this method needs to be called through the object * setAge is the form parameter tag */-(void) setData: (NSString *) name setAge :( int) age; // defines the speak: method-(void) speak: (NSString *) content; // defines a method without parameters-(NSString *) toString; + (void) fuck;

2. Partial implementation Definition

(1) implement partial definition formats

Partial implementation format:

@ ImplementationClassName

{

Type _ variable;

}

-(Type) methodName: (type) param

{

// Method body

}

@ End

(2) Class Name and parent class

Implement partial classification name requirements: The class name is the same as that of the class interface;

Parent class inheritance: If there is a parent class, you can use "@ implementation Class Name: parent class name;

(3) implement partial member variables and member Methods

Declare member variables: If you declare a member variable in the implementation part, the member variable is not accessible externally and can only be accessed in the implementation part;

Member Methods:

--Implement abstract member Methods: Implements the abstract method defined in the interface, that is, the method body for writing some methods of the interface;

--Declare member Method: Declare the member method in the implementation part. The external access is not allowed. access can only be performed in the implementation part;

(4) Example of an abstract Method

Sample Code:

/*************************************** * *********************************> File Name: student. m> Author: octopus> Mail: octopus_truth.163.com> Created Time: 12/14 20:04:28 2014 ************************************ ************************************//** import Student here. the h package is enough, because in Student. the h package has been imported to the Foundation. h header file */# import <Student. h> @ implementation Student {// This member variable defined can only be used in the implementation part. It is a hidden member variable; int _ class;} // defines setData: setAge: method-(void) setData: (NSString *) name setAge :( int) age {_ name = name; _ age = age;}-(void) speak: (NSString) content {NSLog (@ "% @", content) ;}// defines a method with a returned value-(NSString *) toString {return [NSString stringWithFormat: @ "name = % @, age = % d", _ name, _ age] ;}+ (void) fuck {NSLog (@ "fuck") ;}@ end

Ii. Object details

1. object definition, creation, and method call

(1) object definition

Variable definition syntax:Type * Object Name;

--Example: For example, the Student type object defined above,Student * student;

(2) create an object

Create object syntax:[[Class name alloc] initialization method], Example[[Student alloc] init];

--Alloc: Alloc is a keyword, indicating that this is the statement for creating objects. It is equivalent to the new in Java and is responsible for allocating memory space and creating objects;

--Initialization Method: All objects inherit a default initialization method init from NSObject;

Another method for creating objects:[Class Name new], Example[Student new];

--Analysis: This is to take care of the habits of Java programmers and is generally not commonly used;

(3) method call

Method call syntax:[Caller Method Name: parameter 1 parameter label: parameter 2...], Example[Stident fuck];

--Caller: It can be an object or a class, the object calls the instance method, and the class call class method;

(4) Example

Sample Code:

--Code:

/*************************************** * *********************************> File Name: studentTest. m> Author: octopus> Mail: octopus_truth.163.com> Created Time: 12/28 21:58:41 2014 ************************************ ***********************************/# import <foundation/Foundation. h> # import "Student. h "int main (int argc, char * argv []) {@ autoreleasepool {// define the variable Student * student; // create the variable student = [[Student alloc] init]; // method call: Calls class methods. Note that class methods can only be called by classes, but cannot be called by objects. [Student fuck]; // call the method with parameters [student speak: @ "fuck you! "]; // Assign a value to the member variable [student setData: @" Wukong "setAge: 25]; // print the member variable NSString * stuStr = [student toString]; NSLog (@ "Student is: % @", stuStr );}}

--Execution result:

Octopus-2: oc_object octopus $ clang-fobjc-arc-framework Foundation Student. m StudentTest. moctopus-2: oc_object octopus $. /. out 23:22:37. 702. out [415: 507] fuck2014-12-28 23:22:37. 704. out [415: 507] fuck you! 23:22:37. 705 a. out [415: 507] Student is: name = Wukong, age = 25

2. Objects and variables

(1) concepts of objects and pointer Variables

Concept Introduction: Student * student = [[Student alloc] init], which generates the Student object and student variable;

--Object: Creates a Student object;

--Pointer variable: Person is the pointer variable pointing to the object;

(2) storage of objects and pointer Variables

Storage content of objects and variables:

--Object: Stores the member variables of the created Student object;

--Pointer variable: Stores the first address of the object in the heap memory, that is, the first address of the first member variable;

(3) Location of objects and pointer Variables

Storage address of objects and variables:

--Object: Objects are stored in heap memory;

--Pointer variable: Save it in the dynamic storage area of the main () method;

(4) Correspondence between objects and pointer Variables

Correspondence: A pointer can only point to one object, and an object can have multiple pointers pointing to her;

(5) release an object

Memory leakage: If no pointer points to an object, the object must be released; otherwise, memory leakage may occur;

--Solution: Use automatic reference count to place the program in @ autoreleasepool;

3. self keyword

(1) Call the method or variable of the object itself

Call Method: Calls methods or variables of an object;

--Call Method: [Self Method Name: parameter 1 parameter label: parameter 2...];

--Call the member variable itself: Self-> member variable name;

Note:: Self cannot call class methods or class methods. self uses the same method as an object;

(2) Role

Distinguish between member variables and local variables: If the local variable name is the same as the member variable name, use the self-> member variable name to indicate the member variable. The default name is the local variable;

(3) Sample Code

Sample Code: Modify the above Student. m code and run it after compilation. Note that there is a warning. The member variables in the method are the same as the name of the form parameter;

--Code:

/*************************************** * *********************************> File Name: student. m> Author: octopus> Mail: octopus_truth.163.com> Created Time: 12/14 20:04:28 2014 ************************************ ************************************//** import Student here. the h package is enough, because in Student. the h package has been imported to the Foundation. h header file */# import "Student. h "@ implementation Student {// This member variable defined can only be used in the implementation part. It is a hidden member variable; int _ class;} // defines setData: setAge: method-(void) setData: (NSString *) _ name setAge :( int) _ age {// The keyword self-> _ name = _ name; self-> _ age = _ age;}-(void) speak: (NSString *) content {NSLog (@ "% @", content) ;}// defines a method with a returned value-(NSString *) toString {// The self keyword is used to call the method of this object [self speak: @ "The toString method is being called:"]; return [NSString stringWithFormat: @ "name = % @, age = % d ", _ name, _ age] ;}+ (void) fuck {NSLog (@" fuck ") ;}@ end

--Execution result:

Octopus-2: oc_object octopus $ clang-fobjc-arc-framework Foundation Student. m StudentTest. mStudent. m: 21: 16: warning: local declaration of '_ name' hides instance variable [-Wshadow-ivar] self-> _ name = _ name; ^ Student. m: 22: 15: warning: local declaration of '_ age' hides instance variable [-Wshadow-ivar] self-> _ age = _ age; ^ 2 warnings generated. octopus-2: oc_object octopus $. /. out 00:49:46. 7 28 a. out [558: 507] fuck2014-12-29 00:49:46. 730 a. out [558: 507] fuck you! 00:49:46. 731 a. out [558: 507] is calling the toString method: 00:49:46. 731 a. out [558: 507] Student is: name = Wukong, age = 25

4. id type

(1) id type

Id type: Indicates all object types;

--Example: Id student = [[Student alloc] init];

(2) dynamic binding

Dynamic binding: Class to which the trail object belongs. the class to which the object belongs is determined at runtime, and the call method is determined at runtime, not at compilation;

--Usage: A variable of the id type performs dynamic binding when calling a method;

(3) Sample Code

Sample Code:

--Code:

/*************************************** * *********************************> File Name: studentTest. m> Author: octopus> Mail: octopus_truth.163.com> Created Time: 12/28 21:58:41 2014 ************************************ ***********************************/# import <foundation/Foundation. h> # import "Student. h "int main (int argc, char * argv []) {@ autoreleasepool {// define the variable Student * student; // create the variable student = [[Student alloc] init]; // method call: Calls class methods. Note that class methods can only be called by classes, but cannot be called by objects. [Student fuck]; // call the method with parameters [student speak: @ "fuck you! "]; // Assign a value to the member variable [student setData: @" Wukong "setAge: 25]; // print the member variable NSString * stuStr = [student toString]; NSLog (@ "Student is: % @", stuStr );}}

--Execution result:

Octopus-2: oc_object octopus $ clang-fobjc-arc-framework Foundation Student. m StudentTest. mStudent. m: 22: 16: warning: local declaration of '_ name' hides instance variable [-Wshadow-ivar] self-> _ name = _ name; ^ Student. m: 23: 15: warning: local declaration of '_ age' hides instance variable [-Wshadow-ivar] self-> _ age = _ age; ^ 2 warnings generated. octopus-2: oc_object octopus $. /. out 01:09:23. 5 48 a. out [605: 507] fuck2014-12-29 01:09:23. 550 a. out [605: 507] fuck you! 01:09:23. 550. out [605: 507] is calling the toString method: 01:09:23. 550. out [605: 507] Student is: name = Wukong, age = 252014-12-29 01:09:23. 551. out [605: 507] is calling the toString method: 01:09:23. 551. out [605: 507] id is: name =, age = 23