Work with Load Units and Elements

Last modified: July 4, 2023

After finding your unit or element you have to obtain it in its fully-loaded form to be able to change it, or to analyze the information which is not available in just the interface. Changing an element in interface form will result in an exception being thrown.

Each element (whether in interface or full form) has an isLoaded property and load and asLoaded functions. The isLoaded property indicates whether this element is fully loaded already. In practice you should never need to test its value, but simply make sure that you always load a unit/element first.

The load interface loads the element or unit fully. This process is asynchronous. In JavaScript terms, the fully-loaded object is actually the very same instance as the interface, but it is returned from the load method nonetheless, for convenience. The parameter is upcast to the full, non-interface type so that type system (for example, that of TypeScript or your smart IDE) allows access to all members. load always fetches the complete unit, even if you only called it on a specific element. Load always returns units from the local cache if they have already been loaded before.

Since a unit might already have been loaded before, you are also allowed to use asLoaded on an element/unit without arguments in which case it just acts as an upcast from the interface type to the full type. But beware: if the unit that contains that element was not loaded before, an exception will be thrown.

The following (slightly) contrived example demonstrates the behavior of load. The type information is made explicit in this example for demonstration purposes, but you can just omit this code since the TypeScript compiler will infer it. Note that this example is contrived: a normal flow would be to call load on the domainModel and work with the fully-loaded domain model inside its callback.

import {domainmodels} from "mendixmodelsdk";

const model = workingCopy.model();

// at first, only interfaces are available:
const domainModel = model.allDomainModels()[0];
const entity1Interface = domainModel.entities[0];

console.log(entity1Interface.isLoaded); // ==> prints false

const entity1 = await entity1Interface.load();

// entity1 is now the fully-loaded entitiy of type domainmodels.Entity
console.log(entity1.isLoaded); // ==> prints true
console.log(entity1Interface === entity1); // ==> prints true

// loading the entity actually loaded the complete domain model unit:
console.log(domainModel.isLoaded); // prints true
// ... so we can cast it as a fully loaded domainModel:
const fullDomainModel = domainModel.asLoaded();

// In fully-loaded units, all sub elements also have the fully-loaded types,
// while in interfaces all sub objects are interfaces as well.
const entity2: domainmodels.Entity = fullDomainModel.entities[1];
console.log(entity2.isLoaded); // prints true

Continue with How to Generate Code from the Model.

Work with Load Units and Elements

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