Objective-c object-oriented basics, objective-c object-oriented

Objective-c object-oriented basics, objective-c object-oriented

Currently, mobile development is booming. Today, I am studying the recently started Objective-c basic tutorial at home. net is very different. In order to better learn and understand Objective-c, we will record the learning knowledge points in the form of notes for easy reference.

In Objective-c, the class is divided into two parts: declaration and implementation. The Declaration uses the keyword @ interface to implement the use of the keyword @ implementation. The @ symbol can be understood as an extension of the c language, in. net uses the Class keyword, as shown below:

#import <Foundation/Foundation.h>@interface Person : NSObject{    @private    NSString* firstName;    NSString* lastName;}
//getter- (NSString*) firstName;- (NSString*) lastName;
//setter- (void) setFirstName : (NSString*) fName;- (void) setLastName : (NSString*) lName;- (NSString*) description;+ (NSString*) breath;@end@implementation Person-(NSString*) firstName{    return firstName;}-(NSString*) lastName{    return lastName;}-(void) setFirstName:(NSString *)fName{    self->firstName = fName;}-(void) setLastName:(NSString *)lName{    self->lastName = lName;}-(NSString*) description{    return [[self->firstName stringByAppendingString:@" " ] stringByAppendingString:self->lastName];}+(NSString*) breath{    return @"air";}@end

Observe the code and draw the following conclusions:

0. # import the header file. This command can ensure that the header file is only contained once. No matter how many times this command appears in the file, the # include command is used in C.

1. Each method is preceded by a "+" or "-" symbol. + indicates that this method is called by class methods, and-indicates that this method is called by instances.

2. The self keyword table references the instance object itself, which is similar to the this keyword in. NET.

3. NSObject is a base class in Objective-c. We recommend that you inherit NSObject from custom classes. Objective-C does not support multi-inheritance. However, you can implement multi-inheritance through category and protocol.

4. The description method inherits from NSObject and is overwritten in Person. If the instance object is directly used in Objective-c, the description method is called by default, which is equivalent to the ToString in. NET.

5. In Objective-c, the method call is between a pair of square brackets in the form of [instance method: parameter ......].

6. super is used to call the implementation method in the superclass and is used as the call target.

 

NSLog output format characters:

% D	Output integer
% @	Output object. The description method of the object is called by default.
\ N	Line feed

 

 

 

The test code for the Person class is as follows:

Int main (int argc, const char * argv []) {Person * person = [Person new]; [person setFirstName: @ "xiao"]; [person setLastName: @ "ming"]; NSLog (@ "first name: % @", [person firstName]); NSLog (@ "last name: % @", [person lastName]); NSLog (@ "full name: % @", person); // call the description method return 0 by default ;}

The program output is as follows:

The above is the initial understanding of Objective-C. If there are any errors, please point out.