Register a new entity without parameters

Assume that we start from scratch. Let’s create app/util.py:

class Calculator(object):
    def add(self, a:int, b:int) -> int:
        return a + b

At this point, Imagination does not know about the calculator. To do so, let’s register an entity of an instance of app.util.Calculator in containers.xml:

<imagination>
    <entity id="calc" class="app.util.Calculator" />
</imagination>

where calc is the entity ID.

Note

In case you are confused, here is the equivalent code.

from app.util import Calculator

calc = Calculator()

The key differences at this point are:

• the object is not instantiated immediately and is instantiated when the the entity is requested/activated,
• the object is living only in the scope of the container.

How to work with the calculator entity

To refer the calculator entity, for example, in main.py, simply use calculator = assembler.core.get('calc')

Now, to actually use the entity, let’s add something to the end of main.py.

# Omitted the code for main.py already shown above
calculator = assembler.core.get('calc')
result     = calculator.add(123, 456)  # -> int(579)

print(calculator.add(123, 456))  # STDOUT: 579

So, as you can see, the entity works pretty much like a normal object, except the key differences mentioned earlier.

Next step? Register a new entity with parameters.