ios - How to Sort an NSArray of UIColor Objects -

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i wrote class has property of type uicolor called color. how can sort nsarray containing handful of instances of class color property? have tried code below error: [uicacheddevicergbcolor compare:]: unrecognized selector sent instance. best way sort uicolor objects?

nssortdescriptor *sort = [[nssortdescriptor alloc]initwithkey:@"color" ascending:yes]; array = (nsmutablearray*)[array sortedarrayusingdescriptors:@[sort]];

you need use comparator return wether 1 color greater other. 

nssortdescriptor *sort = [[nssortdescriptor alloc]initwithkey:@"color" ascending:yes comparator:^(id obj1, id obj2) {      if (do math determine color bestest) {         return (nscomparisonresult)nsorderedascending;     }else{         return (nscomparisonresult)nsordereddescending;     }  }];

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