Objective-c Study Notes-Basic Content

BOOL

First, write the program:

#import 
 
  BOOL areIntDifferent(int ver1 , int ver2){        if(ver1 == ver2){                return (NO);        }else{                return (YES);        }}NSString* boolString(BOOL yesNo){        if(yesNo == NO){                return (@"NO");        }else{                return (@"YES");        }}int main(int argc , const char *argv[]){        BOOL isDiff;        isDiff = areIntDifferent(6,6);        NSLog(@"are %d and %d different ? %@" , 6,6,boolString(isDiff));        isDiff = areIntDifferent(29,48);        NSLog(@"are %d and %d different ? %@" , 29,48,boolString(isDiff));        return (0);}
 

Then write the GNUMakefile file in the same directory.

include $(GNUSTEP_ROOT)/common.makeTOOL_NAME = CompareTwoNumCompareTwoNum_OBJC_FILES = compare.minclude $(GNUSTEP_ROOT)/tool.make

Run the following command:

Make is compiled successfully. Execute the file./obj/CompareTwoNum and output the following results:

2014-05-06 05:26:58.665 CompareTwoNum[3277] are 6 and 6 different ? NO2014-05-06 05:26:58.666 CompareTwoNum[3277] are 29 and 48 different ? YES

Note: 1. Do not use the following statement in the areIntDifferent function to replace the content in the function.

Return ver1-ver2;

2. Do not compare BOOL values with YES values. It is safer than NO.(1 in OBJC is not equal to YES)

Variable + Loop

#import 
 
  int main(int argc , const char *argv[]){        int count = 3 ;        NSLog(@"the number from 0 to %d is : ",count);        int i ;        for(i = 0 ; i <= count  ; i++){                NSLog(@"%d ", i);        }        return (0);}
 

For details about the GNUMakefile file, see the preceding section.

String operation + strlen (evaluate the string length function)

#import 
 
  int main(int argc , const char * argv[]){        const char * words[4] = {"hello" , "zhangting" , "latitude" , "longitude"};        int count = 4 ;        int i ;        for(i = 0 ; i < count ; i++){                NSLog(@"the length of %s is %d" , words[i] , strlen(words[i]));        }        return 0;}
 

File Operations + strlen

#import 
 
  int main(int argc , const char * argv[]){        FILE * rf = fopen("tmp.txt" , "r");        char word[256];        while(fgets(word,256,rf)){                word[strlen(word) -1] = '\0';                NSLog(@"The length of %s is %d ." , word , strlen(word));        }        fclose(rf);        return (0);}
 

Prepare the tmp.txt file before executing the file.

Fgets reads the line breaks of each line, which occupies the length of one character.

word[strlen(word) -1] = '\0';

Replace the linefeed with the end character of the string.

Message sending representation in objective-c

[Object say]: sends a say message to the object.

New terminology in objective-c

Method: code to respond to a message.

Method Scheduler: a method used by Objective-c to speculate what method is executed to respond to a specific message.

Interface: The operation that the object class should provide.

Implementation: code that allows the interface to work normally.