Post Categories and Tags
In this post, we will discuss taxonomy of posts. Jekyll provides two default Front Matter variables for taxonomy of posts. Categoties are used to build tree-like taxonomy, while Tags are used to build multiple-label taxonomy.
The following official documents are for reference:
Categories
Jekyll provides two variable names for category taxonomy: categories and category. Only use the singular form for personal recommendations. In the plural version, multiple category names are not in a parallel relationship but in a hierarchical relationship. But when using the categories archive function of Minimal Mistakes, this hierarchical relationship will not be reflected.
Spaces in category are considered separators for different category values. If you want to use a single category to represent a hierarchical relationship, you can use / to separate its value. For example:
category: Tech-Note/Personal-Website
It should be noted that category will change the access path of the page. By default, Jekyll sets the access path of posts to include the writing time and title of the file (Minimal Mistakes omits the writing time by default, you can change it by modifying permalink in _config.yml refer to Jekyll DOCS: Permalinks). When category is specified, the post access path consists of category and the title in the file name. In addition, if both category and permalink exist in Front Matter, the access path of the post is determined by permalink.
For example, the access path to this post is:
https://www.zhize.xyz/Tech-Note/Personal-Website/post-categories-and-tags/
https://www.zhize.xyz is my website address.
The file name of this post is 2024-03-31-post-categories-and-tags.md.
The Front Matter of this post is as follows:
---
title: "Post Categories and Tags"
date: 2024-03-31 01:34:29 +0800
category: Tech-Note/Personal-Website
tags: GitHub-Pages Jekyll Front-Matter Minimal-Mistakes
---
Tags
If we use an analogy in object-oriented terms, the taxonomy provided by categories are similar to single inheritance of classes, while the taxonomy provided by tags are similar to multiple inheritance of interfaces.
The variable name of Tags is tags. Spaces are used to separate multiple different tags. Since tags do not change the access address of the post, a post can have multiple tags at the same time. If you wish, you can also use / in tag names to create hierarchical tags.
Generating index
Minimal Mistakes can be indexed based on categories and tags. But this process is not completely automatic. Taking categories as an example, Minimal Mistakes provides a layout called categories. Any page using this layout will automatically display all categories and the posts they contain. However, pages using this layout are not automatically created. You need to create a page yourself and then set it to use categories layout. If you want to implement the function of jumping to the categories index by clicking on its category on the post page, you also need to set the permalink of the index page to /categories/. It should be noted that the index page of categories itself is considered a page, not a post. So please put it in the website root directory or _pages.
Minimal Mistakes also gives an example of a category-archive.md file: https://github.com/mmistakes/minimal-mistakes/blob/master/docs/_pages/category-archive.md.
In order to easily check which posts do not have a category set, you can use defaults in _config.yml to set a default category for all posts (for example Uncategorized).
Under https://github.com/mmistakes/minimal-mistakes/tree/master/docs/_pages you can also find some other examples, such as tag-archive for tags index, year-archive for years index.
It is important to note that these indexes are only effective for posts. If you want to perform similar indexes on other pages, you can use Liquid to implement it yourself.
