Use

mergeDeep is useful when dealing with nested data sources. It will make sure that the right nested objects get updated.

For example, say a Todo and its nested User type are defined as follows:

const User = DefineMap.extend("User",{
    id: "number",
    name: "string"
});

const Todo = DefineMap.extend("Todo",{
    id: {identity: true},
    name: "string",
    complete: "boolean",
    assignedTo: [User]
});

If a todo like the following:

var justin = new User({id: 20, name: "Justin"}),
    ramiya = new User({id: 21, name: "Ramiya"});

var todo = new Todo({
    id: 1,
    name: "mow lawn",
    complete: false,
    assignedTo: [justin, ramiya]
});

is updated with data like:

import {diff} from "diff";
diff.mergeDeep(todo, {
    id: 1,
    name: "mow lawn",
    complete: true,
    assignedTo: [{
        id: 21, name: "Ramiya Meyer"
    }]
})

NOTICE: The todo.assignedTo array removes the Justin todo and updates the Ramiya todo.

Without specifying the identity property of User, the justin instance's id and name will be updated (this is what updateDeep would do):

justin.id //-> 21
justin.name //-> "Ramiya Meyer"

However, if the User object's identity property is specified as follows:

const User = DefineMap.extend("User",{
    id: {identity: true, type: "number"},
    name: "string"
});

When the update happens, the ramiya instance will be updated correctly:

ramiya.id //-> 21
ramiya.name //-> "Ramiya Meyer"