# Creating a Pear Init Template
This guides describes how to create a [`pear init`](../reference/pear/cli.md#pear-init-flags-linktypedesktop-dir) template which can be used to initialize a new Pear application.
## Folder Structure
A template can be initialized from a local directory or P2P (Peer-to-Peer) using a `pear://` link.
A template folder should contain :
* a `_template.json` file which describes the prompt structure.
* a `package.json` file which contains config parameters to be populated from the prompts.
> Note that optionally, if the `package.json` of the parent contains a `main` field it should specify a `__main__` file and a `main` parameter in the `_template.json` file.
Create a template folder called `example` in the project directory, inside the folder create the new files.
```bash
mkdir example
cd example
touch index.html package.json _template.json
```
## Template Structure
Let's define the prompt structure in `_template.json`
### Parameter Object
Each parameter object in the `params` array defines a specific input parameter.
```json
{
"params": [
{
"name": "name",
"prompt": "name"
}
// parameter objects....
]
}
```
Here are the possible fields for a parameter object:
### Required Fields
- `name` (string): The identifier for the parameter. This should be unique within the template.
- `prompt` (string): The text prompt that will be displayed to the user when asking for input for this parameter.
### Optional Fields
- `default` (any): The default value for the parameter if no input is provided.
- `validation` (string): A JavaScript function as a string that validates the input. It should return `true` for valid input and `false` for invalid input.
- `msg` (string): An error message to display if the validation fails.
### Example
Here's an example of a complete parameter object:
```json
{
"name": "main",
"default": "index.html",
"prompt": "Enter the main HTML file name",
"validation": "(value) => value.endsWith('.html')",
"msg": "must have an .html file extension"
}
```
This parameter:
- Has the name "main"
- Defaults to "index.html" if no input is provided
- Prompts the user to enter the main HTML file name
- Validates that the input ends with ".html"
- Displays an error message if the validation fails
Replace the contents of `_template.json` with
```json
{
"params": [
{
"name": "name",
"prompt": "name"
},
{
"name": "main",
"default": "index.html",
"prompt": "main",
"validation": "(value) => value.endsWith('.html')",
"msg": "must have an .html file extension"
},
{
"name": "height",
"validation": "(value) => Number.isInteger(+value)",
"prompt": "height",
"msg": "must be an integer"
},
{
"name": "width",
"validation": "(value) => Number.isInteger(+value)",
"prompt": "width",
"msg": "must be an integer"
},
{
"name": "license",
"default": "Apache-2.0",
"prompt": "license"
}
]
}
```
## App Content
Replace the contents of `index.html` file with :
```html
Initialized from a Pear Template
```
Temporarily set the contents of `package.json` to:
```json
{
"pear": {
"name": "pear-init-template-tutorial",
"type": "desktop"
}
}
```
This is the minimal requirements for a Pear Application `package.json` to run.
This will allow us to test the template's `index.html` as a pear desktop
app.
Run the application using:
```bash
pear run --dev .
```
## Config file
Replace the contents of `package.json` with :
```json
{
"name": "__name__",
"pear": {
"name": "__name__",
"type": "desktop",
"gui": {
"backgroundColor": "#1F2430",
"height": "__height__",
"width": "__width__"
}
},
"type": "module",
"license": "__license__",
"scripts": {
"dev": "pear run -d .",
"test": "brittle test/*.test.js"
},
"devDependencies": {
"brittle": "^3.0.0",
"pear-interface": "^1.0.0"
}
}
```
> Note that any field that is supposed to be populated from the prompts has the value surrounded by double underscores i.e `__fieldName__`
## Initializing a new project
Go to a new project directory and use `pear init` to initialize from the created template.
Run the following command :
```bash
pear init [dir]
```
Here replace `[dir]` with the local template directory path. This can also be a `pear://` link.
This should now initialize a new Pear project from the created template.