How Can I Dynamically Refresh Parts of a Go Template on Variable Updates?

Dynamic Template Refresh on Variable Updates in Golang: A Step-by-Step Guide

There is a need to dynamically refresh a portion of a template when a specific variable is updated, akin to what is possible in Angular.js. In the provided scenario, an AJAX request is made to retrieve addresses based on a postcode, with the results displayed in a section of the template. The goal is to update solely the Addresses value, which is an array, without reloading the entire page.

Solution:

Since the template engine does not support this functionality out of the box, here is a step-by-step guide to achieve it:

1. Refactor Templates:

• Separate the template that renders the Addresses into a distinct block, using either the {{define "name"}} action or the {{block "name"} T1 {{end}} action (Go 1.6 and later).

2. Modify Handlers:

• Create or modify handlers responsible for executing either the full page template or the Addresses template only.
• Send the output of the Addresses template directly to the HTTP response writer.

3. Modify Client Side:

• When the Addresses need to be refreshed, make an AJAX request to the handler that renders only the Addresses template.
• Replace the HTML content of the Addresses wrapper element with the response text of the AJAX request.

Here is a sample JavaScript code that demonstrates this approach:

var e = document.getElementById("addressees");
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
        e.outerHTML = xhr.responseText;
    }
}
xhr.open("GET", "path-to-addresses-render", true);
try {
    xhr.send();
} catch (err) {
    // handle error
}

By following these steps, you can implement dynamic template refresh in Golang, allowing specific portions of the template to be updated when the associated variables change.

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