[Dark horse programmer] ---- simple OC Program

 

1. OC Introduction

• Based on the C language, a minimum object-oriented syntax is added.
• Fully compatible with C language
• The C language code or even c ++ code can be incorporated into the OC code.
• You can use OC to develop Mac OS X and iOS applications.

Ii. OC syntax preview 1. Keywords

• Basically all the keywords are @Start
• The following lists some common keywords. You can just take a look at them. You don't have to go over the information to find their meanings.

@ Interface, @ implementation, @ end

@ Public, @ protected, @ private, @ Selector

@ Try, @ catch, @ throw, @ finally

@ Protocol, @ optional, @ required, @ Class

@ Property, @ synthesize, @ dynamic

Self, super, ID, _ cmd, _ block, _ strong, _ weak,

 

2. the string starts @

For example, @ "hello" is a string in OC, while "hello" is a string in C.

 

3. Other syntaxes

Iii. OC Program Development Process

Similar to C:

 

 

Iv. 1st OC programs 1. Code Writing

Like the C language, the entry to the OC program is still the main function, but it is written to a. m file. For example, it is written to a main. M file (the file name can be Chinese)

1 # include <stdio. h> 2 3 int main () 4 5 {6 7 printf ("1st OC Programs \ n"); 8 9 return 0; 10 11}

 

2. Terminal commands

• Compile CC-C main. m
• Link CC main. o
• Run./A. Out

V. 2nd OC programs 1. Code Writing

Different from the C language, use the nslog function to output content.

1 # import <Foundation/Foundation. h> 2 int main () 3 {4 nslog (@ "2nd OC programs"); 5 return 0; 6}

2. Terminal commands

• Compile CC-C main. m
• Link to CC main. O-framework Foundation
• Run./A. Out

 

3. Differences between nslog and printf

• Nslog receives OC strings as parameters, and printf receives C language strings as parameters.
• Nslog will automatically wrap after output, but not after printf output
• To use nslog, # import <Foundation/Foundation. h>
• To use printf, # include <stdio. h>

 

4. # role of Import

• Like # include, it is used to copy the content of a file.
• It can automatically prevent the file content from being copied multiple times, so that the following preprocessing commands are not required in the header file.

#ifndef     _STDIO_H_#define    _STDIO_H_#endif

5. Role of the foundation framework

• Development of essential frameworks for OC, IOS, and Mac programs
• This framework contains many common APIs (application programming interfaces)
• The Framework contains many header files. If you want to use the content of the entire framework, you can include the main header file.

#import <Foundation/Foundation.h>

6. Use of bool

• Bool type nature

typedef signed char BOOL;

• The bool type has two values: yes and no.

#define YES (BOOL)1#define NO  (BOOL)0

• Bool output (used as an integer)

NSLog(@"%d %d", YES, NO);

Vi. 3rd OC programs 1. Development of multiple. m Files

It is the same as developing multiple. c files in C.

1) write 3 files

• Main. m

1 #import "one.h"2 int main()3 {4     test();5     return 0;6 }

• One. h

void test();

• One. m

1 # import <Foundation/Foundation. h> 2 void test () 3 {4 nslog (@ "test function called"); 5}

2) terminal commands

• Compile: CC-C main. m test. m
• Link: CC main. O test. O-framework Foundation
• Run:./A. Out

2. Mixed Development of. m Files And. c files

1) write 3 files

• Main. m

1 #import "one.h"2 int main()3 {4     test();5     return 0;6 }

• One. h

void test();

• One. c

# Include <stdio. h> void test () {printf ("the test function \ n" is called ");}

2) terminal commands

• Compile: CC-C main. m one. c
• Link: CC main. o one. o
• Run:./A. Out

(If the foundation framework is not used, you do not need-framework Foundation)

VII. Summary

1. # purpose of import:
1> like # include, copy the file content
2> automatically prevents duplicate copies of File Content

2. # import <Foundation/nsobjcruntime. h>
Nsobjcruntime. h contains the nslog function declaration.

3. Path of the header file of the foundation framework
1> right-click xcode. app --> display Package content
2> xcode. APP/contents/developer/platforms/iphoneos. Platform/developer/sdks/iphoneos6.0.sdk/system/library/frameworks/Foundation. Framework

4. Master header file
1> main header file: The main header file, which is generally the same as the framework name and contains all other header files in the framework.
2> the header file name of the foundation framework is foundation. h.
3> you only need to include the main header file of the foundation framework to use the entire framework.


5. Running Process
1> write OC source files:. M,. c
2> compile: CC-c xxx. m xxx. c
3> link: cc xxx. o xxx. O-framework Foundation
(The-framework foundation must be added only when the foundation framework is used)
4> Run:./A. Out