Overriding methods using Transcrypt

Question

In Python it is valid to override a method, like:

class A():
    def original(self):
        print("original")

def alternative(self):
    print("alternative")

A.original = alternative
a = A()
a.original()

which will print alternative. But after transpilation to Javascript you'll get the error: Uncaught TypeError: Cannot set property original of function....

Of course this has to do with the fact that it is transpiled to:

var A = __class__ ('A', [object], {
    __module__: __name__,
    get original () {return __get__ (this, function (self) {
        print ('original');
    });}
});

where original is a property which cannot be overriden in this way.

Is there a workaround for this? It can be useful in some cases to have this behaviour. Best regards

Answer 1

The following workaround will do the trick:

class A():
    def original (self, anArg):
        print ('Original:', anArg)

def alternative (self, anArg):
    print ('Alternative:', anArg)

a0 = A ()
a0.original ('Time flies like an arrow.')

__pragma__ ('js', '{}', '''Object.defineProperty (A, "original", {
    get: function (self) {return __get__ (this, alternative)}
})''')

a1 = A()
a1.original ('Fruit flies like a banana.')

It will print:

Original: Time flies like an arrow. Alternative: Fruit flies like a banana.

I've added an argument to illustrate the generality of his solution.