MTL Code Generation

Code Generation from Models

Learn how to load models and navigate them in MTL templates to generate code based on metamodel structure.

In this tutorial, you’ll work with the Company metamodel from earlier tutorials, loading model instances and generating Swift code from them.

40 mins Estimated Time

Section 1

Loading Models in Templates

MTL templates can reference metamodels and navigate loaded model instances. The module declaration specifies the metamodel URI, and template parameters define model types.

This connects your templates to actual model data, enabling true model-driven code generation.

Step 1

Declare a metamodel-aware module.

The module declaration now references the Company metamodel’s nsURI. This lets MTL understand the metamodel’s structure.

CompanyGenerator.mtl

1[module CompanyGenerator('http://www.example.org/company')]

Step 2

Create a template that accepts a model element.

The template parameter c : Company indicates this template expects a Company model element. You can access the element’s properties using dot notation.

CompanyGenerator.mtl

1[module CompanyGenerator('http://www.example.org/company')]
2
3[template main(c : Company)]
4Company: [c.name/]
5[/template]

Step 3

Generate code from the model.

Pass both the template and model file to swift-mtl. It loads the model and executes the template with the root element.

Terminal

1swift-mtl generate CompanyGenerator.mtl --model company-model.xmi --output generated/

Section 2

Navigating Model References

Models contain references to other elements. Navigate them using dot notation—the same way you access properties in Swift.

MTL automatically follows containment and non-containment references, letting you traverse the entire model graph.

Step 1

Access referenced elements.

Use dot notation to navigate from Company to employees. MTL understands the metamodel’s references and provides access to related elements.

CompanyGenerator.mtl

1[module CompanyGenerator('http://www.example.org/company')]
2
3[template main(c : Company)]
4Company: [c.name/]
5Employees: [c.employees->size()/]
6[/template]

Step 2

Iterate over collections.

The for directive iterates over collections. Each iteration binds the variable to one element, letting you generate code for each item.

CompanyGenerator.mtl

1[module CompanyGenerator('http://www.example.org/company')]
2
3[template main(c : Company)]
4Company: [c.name/]
5
6Employees:
7[for (emp : Person | c.employees)]
8  - [emp.name/] ([emp.email/])
9[/for]
10[/template]

Check Your Understanding

Question 1 of 1

How do you specify that a template works with a specific metamodel?

In the module declaration using the metamodel’s nsURI

Correct! The module declaration’s URI parameter should match the metamodel’s nsURI from its Ecore definition.

Using an import statement

Incorrect. MTL doesn’t use import statements. The module declaration establishes the metamodel connection.

In the template parameter types

Incorrect. Parameter types use the metamodel’s classes, but the module declaration establishes which metamodel is active.

Protected Areas

Learn how to preserve manual code changes across regenerations using protected areas.

Get started