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Docs: template-unreal

Quick-Start

The Quick-Start guide explains how to, in few steps, get from an API to a functional Unreal Engine plugin.

1. Install the Code Generator​

ApiGear provides two powerful tools: a Studio and a Command Line Interface (CLI). The Studio is a graphical tool for creating, editing API modules and projects, while the CLI is a command-line tool for generating code from API modules. Both offer comprehensive functionality, including SDK template management, API project creation, code generation, API monitoring, and API simulation.

Download Studio
Download CLI

Install ApiGear Studio​

ApiGear Studio is available for macOS, Windows, and Linux. You can download it from the ApiGear Studio GitHub releases page.

For more detailed information on ApiGear Studio, refer to the dedicated studio documentation.

Install ApiGear CLI​

The ApiGear CLI is a versatile command-line tool for generating code from API modules. It's available for macOS, Windows, and Linux. Download the latest version from the ApiGear CLI GitHub releases page.

The CLI offers all the features available in the Studio.

For more detailed information on the ApiGear CLI, consult the dedicated CLI documentation.

2. Obtain the Template​

There are several methods to obtain the template: installation via the Studio, installation via the CLI, or cloning/downloading from GitHub.

This step is optional

The ApiGear Studio and the CLI detect the specified template in the solution document and install it automatically.

Optional steps (click to expand)

Installation via CLI​

When using the CLI, only the highlighted line needs to be executed. You can verify the successful installation using the template cache command.

$ apigear template install apigear-io/template-unreal@v3.2.2
$ apigear template cache
list of templates from the local cache

source                            | url                                               | installed | latest
apigear-io/template-unreal@v3.2.2 | https://github.com/apigear-io/template-unreal.git | <sha1>    | v3.2.2
...

Installation via Studio​

Installing the template through the Studio is straightforward:

  1. Open an existing project or create a new one
  2. Navigate to the Templates tab
  3. Click Install on the apigear-io/template-unreal entry
Installing the template
Figure: Installing the template

Cloning from GitHub​

If you need to inspect or modify the template's source code, cloning or downloading the repository is recommended. The repository doesn't need to be part of your project and can be stored anywhere on your computer.

$ git clone https://github.com/apigear-io/template-unreal.git

You can then configure the solution file to use your template by providing the relative path from the solution file to the template directory.

3. Set Up the Project​

A typical project requires two files: a solution file specifying the APIs and the template to use, and at least one API module file. Ideally, both should be placed in a folder named apigear, adjacent to each other.

Alternatively, you can use the Studio to create a new project and modify the two example files provided.

Solution File​

Create a solution file. The example below specifies:

  • Module files in line 8, here the helloworld.module.yaml module with the Hello API
  • The output directory for generated files in line 9
  • The template used to generate the code in line 10 (this can also be a path to a local copy of the template)
  • The enabled features of the template in line 13, here the stubs feature, which provides a simple implementation of interfaces.
helloworld.solution.yaml
schema: "apigear.solution/1.0"
name: hello_world_example
version: "0.1.0"

targets:
  - name: ue_docs
    inputs:
      - helloworld.module.yaml
    output: ../ue_docs
    template: apigear-io/template-unreal@v3.2.2
    force: true
    features:
      - stubs
Targets

You can extend this solution file with additional targets, each for a different technology with a different template. The module.yaml file is technology-independent and can be used with any template.

Template Version

We highly recommend specifying the exact version of the template. Otherwise, a newer version will be automatically downloaded and used for code generation. This can lead to unexpected behavior if file structures or code changes in the template.

note

Set the force parameter to true if you want to always override all generated files. When set to false, some files, such as implementations (stub feature), won't be updated. API files are always updated regardless of this setting.

API Module File​

Use your preferred text editor to create the helloworld.module.yaml file with the following example content:

helloworld.module.yaml
schema: apigear.module/1.0
name: io.world
version: "1.0.0"

interfaces:
  - name: Hello
    properties:
      - { name: last, type: Message }
    operations:
      - name: say
        params:
          - { name: msg, type: Message }
          - { name: when, type: When }
        return:
          type: int
    signals:
      - name: justSaid
        params:
          - { name: msg, type: Message }
enums:
  - name: When
    members:
      - { name: Now, value: 0 }
      - { name: Soon, value: 1 }
      - { name: Never, value: 2 }
structs:
  - name: Message
    fields:
      - { name: content, type: string }

4. Generate Code​

Generate via CLI​

The following snippet demonstrates how to run the CLI and provides an example output:

$ apigear generate solution apigear/helloworld.solution.yaml
10:52:20 INF generated 21 files in 30ms. (20 write, 0 skip, 1 copy) topic=gen
  • The generate command instructs the CLI to generate code
  • The solution parameter specifies that we want to process a solution file

Generate via Studio​

  1. Open the project
  2. Navigate to the Solutions tab
  3. Click Run on the helloworld.solution.yaml entry
Generating code
Figure: Generating code

5. How to use the plugin​

Project folder structure​

For the code generation we assume that both ApiGear files reside in an apigear subfolder next to the Unreal Engine project. In this case the folder structure should look similar to this.

📦ue_docs_example_project
 ┣ 📂apigear
 ┃ ┣ 📜helloworld.solution.yaml
 ┃ ┗ 📜helloworld.module.yaml
 ┣ 📂ue_docs
 ┃ ┣ 📂Config
 ┃ ┣ 📂Content
 ┃ ┣ 📂Platforms
 ┃ ┣ 📂Plugins
 ┃ ┣ 📂Source
 ┃ ┗ 📜ue_docs.uproject

Using the solution file from the previous paragraph the code will be generated in the ue_docs/Plugins folder.

Prerequisites

This guide assumes you already have an Unreal Engine project. The generated plugin will be placed in your project's Plugins folder.

The generated code can be used with Blueprints and C++. Make sure to have the generated plugin code in your projects plugins directory as noted in the previous section.

Verify Plugin Installation​

After generating the code:

  1. Open your Unreal project in the Editor
  2. Go to Edit → Plugins
  3. Search for IoWorld - you should see the generated plugin listed
  4. Ensure the plugin is enabled (checkbox checked)
  5. Restart the Editor if prompted

If the plugin does not appear, verify the generated files are in the correct Plugins folder and regenerate project files.

Using the Interface​

Getting the Subsystem​

Open your project in the Unreal Editor and choose a Blueprint where you want to use the interface. First, get the GameInstance subsystem of the type IoWorldHelloImplementation:

Get subsystem in Blueprint
Figure: Get subsystem in Blueprint

Calling Operations​

On this subsystem we can choose the asynchronous Say function. Using the async version prevents blocking the game thread:

Choose method on interface in Blueprint
Figure: Choose method on interface in Blueprint

Complete Example​

The complete setup to say "Hello world" on begin play:

Hello interface example in Blueprint
Figure: Hello interface example in Blueprint

Subscribing to Events​

To react to property changes or signals in Blueprints:

  1. Get the subsystem as shown above
  2. Call Get Publisher on the subsystem
  3. From the Publisher, drag off and search for Assign to find bindable events
  4. Choose the event you want: On Last Changed BP (property change) or On Just Said Signal BP (signal)

The Publisher object holds all delegates because Unreal interfaces cannot declare delegates directly.

note

Blueprint screenshots for event binding coming soon.