CoffeeScript Question
Coffeescript tree extends class not working
I need to create a tree that, for example CALCULATE 2 numbers. I do in coffee script, who connvert javascript due to extend class.
class Expression
@Evaluate = -> 0
class Const extends Expression
constructor: (value)->
class BinaryOperation extends Expression
constructor: (L, R)->
class Add extends BinaryOperation
@Evaluate = -> L.Evaluate() + R.Evaluate();
expr = new Add(new Const(10), new Const(10));
alert(expr.Evaluate())
Demo: https://jsfiddle.net/f3ry/D9kBP/24/
Thanks.
Answer Source
Your problem is a combination of syntax errors and a misunderstanding of how subclassing works. This should get you there:
class Expression
Evaluate: () -> 0
class Const extends Expression
constructor: (@value) ->
Evaluate: () -> @value
class BinaryOperation extends Expression
constructor: (@L, @R)->
class Add extends BinaryOperation
Evaluate: -> @L.Evaluate() + @R.Evaluate();
expr = new Add(new Const(10), new Const(10));
alert(expr.Evaluate())
Adding the @ to the constructor parameter sets it as a property of the newly created object. Overriding the Evaluate method allows the operations to be performed. Link to example.