Dynamic Navigation (Example)

Overview 

We assume you already created a new app to work in.

This tutorial will cover:

• Dynamic routing
• Templates

Step 1: Add the Route 

For this example, instead of relying on the automatic page URL, we want to include a dynamic color name in the URL.

Edit app/settings/app.jcon and modify the routes block so that it looks like this:

routes: {
    /colors/{color}: colors.tht
}

Step 2: Create the Page 

Create a new file: pages/colors.tht.

Copy and paste the following code:

// THT will automatically call main() when the page loads.
function main() {

    // Get the current color from the URL
    let pageColor = Input.route('color');

    print('color: ' ~ pageColor);
}

Load the page to make sure it works:
http://localhost:8888/colors/red

You will see something like this:

(Try changing the color in the URL.)

Step 3: Add a Template 

Now let’s send the page back as HTML, using a template.

First, we replace the print line with a call to Response.sendPage, which sends a complete HTML document.

In the css field, we tell it to use THT's built-in Base Stylesheet.

Replace the content of colors.tht with this code:

function main() {

    let pageColor = Input.route('color');

    Response.sendPage({
        body: pageHtml(pageColor),
        css: Css.plugin('base'),
    });
}

template pageHtml(color) {

    <main style="border-top: solid 2rem {{ color }}">
        <h1>{{ color.toUpperCaseFirst() }}</>
    </>
}

This is what you should see when you refresh the page:

Step 4: Add Navigation Links 

Create a new function that returns a list of colors.

By keeping this list separate from the template, it will be easier to change later on.

function getLinkColors() {
    return ['red', 'aqua', 'orange'];
}

Then update the page template to include a new template that creates a link to each color.

The -- double-dash symbol is used to embed lines of THT code.

template pageHtml(color) {

    <main style="border-top: solid 2rem {{ color }}">
        <h1>{{ color.toUpperCaseFirst() }}</>

        {{ linksHtml() }}
    </>
}

template linksHtml() {

    -- for (linkColor in getLinkColors()) {
        <a href="/colors/{{ linkColor }}">
            {{ linkColor.toUpperCaseFirst() }}
        </> &nbsp;
    -- }
}

This is what you should see when you refresh the page:

Step 5: Experiment 

Try changing and expanding the code to see what happens.

Ideas:

• Add new colors, like turquoise and gray.
• Modify /pages/css.tht and remove the call to Css.plugin. See what the page looks like without it.
• If the route has a color that is not in the list of links, call Response.sendError(404).