First lecture, Class and Object

First, OC overview

Code format

int main (int argc, const char * argv[]) {
@autoreleasepool {

Code Area

}
return 0;
}

1, OC support basic data type int, float

2. Use string Object @ "Hello" in the string "Hello" oc in C language

3, NSString is provided by the System class Library--String class
The variable that defines the object type must be added * NSString * name = @ "Zhangyixing";

4. New Type class type (object type) in OC

5, printf (C) NSLog (OC) Output string content NSLog (@ "zhangyixing");

6, output the value of the basic data type
NSLog (@ "number =%d, score=%.2f, age =%ld", number, score, age);

7. Output Object
NSLog (@ "name =%@", name); NSLog (@ "name =%@", @ "zhangyixing");

Second, object-oriented programming

Object-oriented programming oop (Object Oriented programming)

Object-oriented language: c++,java,c#

Concepts: objects, classes, encapsulation, inheritance, polymorphism, etc.

III. Classes and objects

Define the class first, then create the object, and use the object.

A class is a template, and an object is a concrete representation of any object that consumes memory space.

1, the definition of the class----interface part, implementation part

New file OS X-------Cocoa CALSS

Set Name:person (name file with class name), subclass Of:nsobject, Language:oc

1) interface part----The characteristics and behavior of the external declaration----------Person.h File

#import <Foundation/Foundation.h>

Start of the interface

@interface Person:nsobject (class name: Parent type)

{

Declaring the characteristics of a class

Instance variables: Stores the characteristics of an object note: The first letter is _

NSString * _NAME;

int _age;

}

Declaring the behavior of a class

Method: Similar to the function in C, the concept of no function in OC

(1) + indicates that this method belongs to a class, only class execution [class name Method name]

(2)-Indicates that this method belongs to an object and only the object executes [object method name]

-(void) sayhi;

End of interface

@end

2) Implement partial----internal implementation----------PERSON.M file

#import "Person.h"
The beginning of the implementation section
@implementation person
-(void) sayhi//minus spaces
{
NSLog (@ "Hello");
}

End of implementation
@end

2. Create object: Allocate memory space, initialize, heap area-------main.m file

The main function imports the file----#import "Person.h"

1) allocating memory space---[Class name alloc]
Using the [] Call method in OC Alloc is a method that the system-supplied class can invoke
(1) Allocating memory space in the heap area;

(2) The data of the memory space is cleared automatically, and the default value of all instance variables is set to 0;

(3) Return the first address of the allocated storage space

Person * p1 = [Person alloc];
The pointer P1 points to the person object stored in the heap area, so the P1 is usually referred to as the person object

2) Initialize object------[Object init]

Initialize: Sets an initial value for an instance variable of an object

Init initialization is a system-provided method of object initialization that can only be called by an object

P1 = [P1 init];
Person * p2 =[[person alloc] init];
P1 p2 are of the same type, two different objects

Person * P3 = nil; P3 points to NULL, is a null pointer and cannot be treated as an object

In OC, any operation on nil is invalid.

P3 = p1; P3, P1 point to the same object

3, through the object invocation method, realizes the function

Using the [] Call method in OC Alloc is a method that the system-supplied class can invoke

[P1 Sayhi]; Print----Hello

This article is from the OC Learning Notes blog, so be sure to keep this source http://10613955.blog.51cto.com/10603955/1684156

First lecture, Class and Object