SpaceDog SpaceDog - 12 days ago 9
iOS Question

Inability to create my CIFilter classes from string

After creating this question myself about the inability to create my own UIImageView classes by name I am facing a similar problem, this time for CIFilter subclasses that are not solved by the accepted answer on the other question.

Said that, this is the problem.

I am creating subclasses of

CIFilter
class, something like
MyEffectFilter1
,
MyEffectFilter1
, etc.

These subclasses have this convenience method for the creation of specific images:

+ (instancetype)novo {
MyEffectFilter1 * newFilter = [self filterWithName:...
// do stuff
return newFilter;
}


When I try to create such classes using this new command by string

id newObject = [NSClassFromString(nameOfClass) novo];


And verify the created objects, I see that their classes are not the ones I create but CIFilter ones. For example: if I create a Comic filter using my created class:

// initialization code on MyComicClass.m
+ (instancetype)novo {
MyComicClass * newFilter = [self filterWithName:@"CIComicEffect"];
// do stuff
return newFilter;
}


By doing

id newObject = [NSClassFromString(@"MyComicClass") novo];


and do a
po newObject
to console, or test the class using

Class class = [newObject class];


I get class equal to
CIComicEffect
not
MyComicClass
.

Any ideas on how to solve this?

Answer

In this case, the subclass constructor is trying to call the inherited class's convenience constructor (in contrast with the previous question, which was calling the inherited init).

Change your constructor to do the analogous thing, calling alloc on self. It doesn't look like CIFilter provides any public initWith... methods, but a property such as name can be set easily enough by calling the new instance directly...

// MyEffectFilter1.m
+ (instancetype)novo {
    MyEffectFilter1 *newFilter = [[self alloc] init];
    newFilter.name = @"name";
    return newFilter;
}

I tested that code as follows...

MyEffectFilter1 *filterA = [MyEffectFilter1 novo];
MyEffectFilter1 *filterB = [NSClassFromString(@"MyEffectFilter1") novo];

In lldb, these inspect as follows...

enter image description here