Let’s talk about how to use the templates package in golang

Go is a rapid development programming language with simple syntax and powerful concurrency features, making it ideal for web development. In web development, templates are an integral part because they enable dynamic generation of HTML pages and provide users with interactive web interfaces. Go provides a package called templates for dynamically generating HTML pages. This article will introduce the usage of golang templates.

Template

A template in golang templates is a string or byte array containing tags or placeholders that will be replaced with the actual ones when rendering value. In addition, templates may contain control structures and function calls.

Template engine

Golang templates uses an analysis-based template engine, which can analyze templates and generate HTML pages based on the analysis results. The parser breaks the template into fragments and represents them as a tree of nodes. Each node represents a part of the template, such as text, control structures, variables, paired tags, etc. The relationship between nodes is a tree structure relationship from parent node to child node.

Tags and placeholders

Tags and placeholders in templates are included using {{}}. For example: "{{ . }}" means using the current context variable. A template can define multiple variables and access them through a special context object. Context objects are stored in associated golang templates.

Control structure

Golang templates support the following control structures:

• {{if}} control structure, used to control conditional statements
• {{for}} control structure, used for looping and iteration
• {{range}} control structure, used for iterating over collections

Here is a demonstration of how to use {{if} } and {{range}} control structures:

{{if .HasValidUsers }}
    <h1>Welcome Valid User</h1>
{{end}}
{{range .Users}}
    <li>{{ .Name }}</li>
{{end}}

In this example, we use {{if}} to check if there is a valid user and {{range}} to iterate through the user list.

Function call

In golang templates, you can also call other functions, such as string formatting functions, and arithmetic and logical operators. For example, the following example demonstrates how to use a template to call the printf function.

{{ printf "%s is %d years old" .Name .Age }}

In this example, we called the printf function, passing the text string and the values ​​of the objects .Name and .Age to the printf function.

Types and methods

Golang templates support types and methods through the reflect package. The reflect package is a Go language standard library for runtime reflection and type information. We can use the reflect package in the template to query the type and method of the value and perform operations based on the query results. Here is an example of a template that outputs the type of an object as an HTML comment:

<!-- {{ printf "# Type: %s" . | typeOf | name }} -->

In this example, we use types and methods to query the type of an object and output its name.

Handling whitespace

Golang templates use whitespace characters (including spaces, tabs, and newlines) to build generated HTML pages. However, in the generated HTML page, whitespace characters may affect layout and display. In order to control the display of whitespace characters, we can use the trim function to remove whitespace characters. For example, in the following example, we use the trim function to remove the spaces around the title:

{{- $title := " Hello World " -}}
<h1>{{- trim $title -}}</h1>

In this example, we use the {{-}} notation to remove the spaces between variables and functions, and use trim Function removes spaces around the title.

Summary

This article introduces the usage of golang templates. golang templates is a lightweight yet powerful tool that supports control structures, type and method queries, and other rich features. We can use it to dynamically generate HTML pages and provide a complete and flexible interface for web applications. Hope this article is helpful for beginners!

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