Re: Call-Super antipattern
Philipp wrote:
Hello,
I just read about the "Call-Super" antipattern
(http://en.wikipedia.org/wiki/Call_super) and I'm not completely
convinced about the "anti-pattern" property of this construct.
Suppose you have a class hierarchy which makes sense, something like:
Car extends Vehicle
Ford extends Car
and they all have a start method:
Why is it bad for each start to call the super method? (in case each one
adds the super's behavior)
In particular, a proposed solution in the wiki article is to use the
template method pattern. How does that improve the design? In a
multi-inheritance structure as this example, you will still have to
choose between replicating code (Copy-Paste antipattern) or adding
template methods (hooks) for all possible subclasses.
Thanks for your comments.
Philipp
public class Vehicle {
public void start(){
// unlockDoor();
}
public static class Car extends Vehicle {
@Override
public void start() {
super.start();
// startEngine();
}
}
public static class Ford extends Car {
@Override
public void start() {
super.start();
//switchRadioOn();
}
}
}
<rant>
First, The "Ford is-a Car" is an example of a terrible design. A Car
has-a Make and has-a Model, Ford is a Make, FordModelT is a Model. Think
about it, would you want to maintain the class hierarchy that contains
RedHondaCivicWithSpoiler.
</rant>
Despite that, a framework should rely as little as possible on consumers
to "do the right thing". The right way to do it is to have an
protected overridable method that isn't expected to call super, and the
non-overridable public method that delegates to the appropriate.
In other words, the work-flow should be defined by the class higher in
the hierarchy, and the details by the lower.
--
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