How to implement interface method with different type parameter

tl;dr

I need to have TypeInterface::generateId(<object> $doc) where the <object> is different for each class that implements the interface

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Hi guys

I'm wrecking my head with this.

I have an interface (TypeInterface) which needs to have a method like TypeInterface::generateId(Document $doc) that will return a generated id from the doc specs, so far so good.

the problem

The several documents have methods in common, like ::schema(), but all the properties are specific for each one. So from this I made the following interfaces

• DocumentInterface - holds the methods that all documents must have
• ObjectAInterface - holds the methods for the properties of Document type A
• ObjectBInterface - holds the methods for the properties of Document type B

So the class TypeA (which implements TypeInterface) generates the ID with some properties/methods of ObjectAInterface that ObjectBInterface doesn't have for the TypeB class

Questions:

• How can I achieve this?
• Best practices in these cases?

code

I've created a simple gist with the example code http://ift.tt/1FV1ljL