objective-c Medium Categary( Category ) It's quite widely used , Its connotation is similar to javascript Medium prototype, Methods that can extend a class .

Here's a basic example , Reference resources oc Programming book :

  • Achieve one categary
#import <Foundation/Foundation.h>
@interface NSString(Util) // stay NSString On the basis of Util Category
#import "NSString+Util.h"
@implementation NSString(Util)
if([self hasPrefix:@"http"]){
return TRUE;
return FALSE;
} @end
  • Test code
#import <Foundation/Foundation.h>
#import "NSString+Util.h" // Include header files and start using this category int main(int argc, const char * argv[]) {
@autoreleasepool {
NSString *test1 = @"http://lcacds";
NSString *test2 = @"fdsfs"; if([test1 isUrl]){ // Judge whether it is a URL link
NSLog(@"%@ is url", test1);
NSLog(@"%@ not url", test1);
} if([test2 isUrl]){
NSLog(@"%@ is url", test2);
NSLog(@"%@ not url", test2);
return ;

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