Composing trees

In MST, every node in the tree is a tree itself. Trees can be composed by composing their types:

const TodoStore = types.model({
    todos: types.array(Todo)
})

const storeInstance = TodoStore.create({
    todos: [{
        title: "Get biscuit"
    }]
})

The snapshot passed to the create method of a type will recursively be turned into MST nodes. So you can safely call:

storeInstance.todos[0].setTitle("Chocolate instead plz")

Because any node in a tree is a tree in itself, any built-in method in MST can be invoked on any node in the tree, not just the root. This makes it possible to get a patch stream of a certain subtree, or to apply middleware to a certain subtree only.