Magic Contexts

In the Store guide, we briefly mentioned that Store objects can be used with the mk.magic context.

In this section, we will:

• Explain what the magic context is

• Show how to use the magic context

• Show limitations of the magic context

• Understanding alternatives to the magic context

• Understand best practices for magic

What is the magic context?

Important

Use the mk.magic context to make methods and attribute access on Store objects reactive.

The magic context is a special context in which methods and attribute access for Store objects become reactive.

This means that you can use Store objects in a more natural way, without having to worry about whether or not the statement you’re writing is reactive.

Example

For example, consider an object Greeting that has an attribute name and a method get_intro.

class Greeting:
    def __init__(self, name):
        self.name = name

    def get_intro(self):
        return f"Hello {name}!"

Typically, accessing attributes of the wrapped object and calling methods on the wrapped object are not reactive.

greeting = mk.Store(Greeting("Meerkat"))

# Neither of these statements are reactive.
name = greeting.name
intro = greeting.get_intro()

# Even when we indicate the store has updated,
# the statements above are not reactive, so they
# wont update.
greeting.name = "Rhino"
greeting.set(Greeting("Rhino"), triggers=True)

With the magic context, we can access name and call get_intro method in a reactive way.

greeting = mk.Store(Greeting("Meerkat"))

with magic():
    name = greeting.name
    intro = greeting.get_intro()

# Now, when we update the store, the statements above
# will update.
greeting.name = "Rhino"
greeting.set(Greeting("Rhino"), triggers=True)

print("name:", name)
print("intro:", intro)