iOS realizes the function that the picture exists locally and then gets the picture locally

iOS realizes the function of local picture existence and local picture acquisition. The code is as follows:

// Save pictures locally 
+ (void)SaveImageToLocal:(UIImage*)image Keys:(NSString*)key {
 NSUserDefaults* preferences = [NSUserDefaults standardUserDefaults];
 //[preferences persistentDomainForName:LocalPath];
 [preferences setObject:UIImagePNGRepresentation(image) forKey:key];
}
 
// Are there any related pictures locally 
+ (BOOL)LocalHaveImage:(NSString*)key {
 NSUserDefaults* preferences = [NSUserDefaults standardUserDefaults];
 //[preferences persistentDomainForName:LocalPath];
 NSData* imageData = [preferences objectForKey:key];
 if (imageData) {
  return YES;
 }
 return NO;
}
 
// Get pictures locally 
+ (UIImage*)GetImageFromLocal:(NSString*)key {
 NSUserDefaults* preferences = [NSUserDefaults standardUserDefaults];
 //[preferences persistentDomainForName:LocalPath];
 NSData* imageData = [preferences objectForKey:key];
 UIImage* image;
 if (imageData) {
  image = [UIImage imageWithData:imageData];
 }
 else {
  NSLog(@" Picture not obtained locally ");
 }
 return image;
}