When using AnQiCMS for website content management, we often need to process the displayed data in the template to ensure that the content presentation is both beautiful and conforms to business logic.A common requirement is that when certain text content (such as product model numbers, article titles, or image file names) is prefixed with a specific prefix, but we want to remove this prefix when displaying on the front end while retaining the rest of the text.For example, our product model numbers may all start with a prefix '-' but we only want to display the model itself when presented to the public.

This question seems simple, but the key is to distinguish between 'removing a specific character from the beginning of a string' and 'removing all specific characters from a string'.AnQiCMS powerful template engine is based on Django template syntax, providing a variety of filters (filters) to handle strings, one of which is specifically designed to solve this kind of problem.

Background of the issue: The necessity of precisely removing the prefix of a string

Imagine such a scenario: To facilitate internal management and data classification, we have added department tags to each product model in the background, such as 'Research and Development Department - Product A', 'Marketing Department - Product B'.But when facing customers on the website front-end, displaying "R&D Department - Product A

If simply using the global replacement feature to replace 'R&D-' with nothing, then if the product description also contains the term 'R&D-', it will be removed as well, which is clearly not the result we want. We need a feature that can identify and only removeString startA method with a specific prefix.

AnQiCMS solution:trimLeftFilter

AnQiCMS template engine provides for such needs.trimLeftFilter. This filter is specifically designed to remove the specified characters or strings from the beginning of a string. Its design purpose is to accurately handle this 'prefix removal' task.

trimLeftThe working principle of the filter:

trimLeftIt will check if the beginning of the string contains the specified "keyword" (this keyword can be a single character or a complete string).If it contains, it will remove the matching prefix part.trimLeftNo operation will be performed, thus perfectly avoiding the issue of mistakenly deleting non-prefix content.

Usage:

trimLeftThe basic syntax of the filter is very intuitive:

{{ 你的变量 | trimLeft:"要移除的前缀字符串" }}

Let us take the example mentioned at the beginning of the article as an example, assuming your product model is stored initem.Titlethe variable, and it starts with the prefix "-", we want to remove this prefix:

{# 假设 item.Title 的值为 "前缀-商品名称XYZ" #}
<p>原始商品名称：{{ item.Title }}</p>
<p>处理后商品名称：{{ item.Title | trimLeft:"前缀-" }}</p>

Show results:

原始商品名称：前缀-商品名称XYZ
处理后商品名称：商品名称XYZ

As you can see,trimLeftThe filter accurately removed the prefix '-' from the beginning of the string without affecting the rest.

If you need to remove is not a fixed prefix, but a set of variable prefixes (for example, some products may start with "prefixA-trimLeftor selectively apply based on business logic. However, for removing fixed prefixes,trimLeftis undoubtedly the simplest and most efficient solution.

WhytrimLeftis**selective

In AnQiCMS templates, although there are stillcutandreplacesuch string processing filters,trimLeftthey have different functional orientations:

  • cutFilter: cutused to delete strings fromallThe specified character appears. If you want to remove all spaces from the string,{{ "Hello World" | cut:" " }}You will getHelloWorldIf used to delete the prefix, it will delete all matching characters in the string, which does not meet our requirement of only deleting the prefix.
  • replaceFilter: replaceUsed to replace a specific keyword in a string with another keyword. Although it is theoretically possible to achieve this through complex regular expressions or other programming means, the prefix replacement in AnQiCMS templates isreplaceThe filter typically performs global replacement, i.e., replacing all matching keywords. Therefore, it also cannot meet the precise requirement of deleting specific characters only at the beginning of the string.

In contrast,trimLeftThe filter is designed by AnQiCMS specifically for handling leading characters of strings, it can accurately locate and remove the matching strings at the beginning, which is the most direct and effective way to solve this problem.

Practice scenarios and more possibilities

trimLeftThe application of it is not limited to product models and article titles. In actual website operations, you may use it in the following scenarios:

  • Image file name processing:After the image is uploaded, the system automatically adds a timestamp or a user ID as a prefix, such as '20231026-image.jpg'.trimLeftRemove the timestamp prefix.
  • Optimize URL alias:Some URL paths may have fixed category prefixes, but in certain specific display modules, you may want the URL links to appear simpler, showing only the part without the prefix.
  • List data cleaning:When displaying data lists, if some fields in the data source have unnecessary descriptive prefixes (such astrimLeftCan help you quickly clean data, improve the readability of content.

Understand and master the use oftrimLeftFilter, making your AnQiCMS template more flexible, efficient, and presenting refined content that meets user expectations.

Common Questions (FAQ)

  1. trim/trimLeftandtrimRightWhat are the differences between filters? trimThe filter is used to remove all leading and trailing spaces or specified characters from a string. For example,{{ " 你好 " | trim }}Will become"你好"If a character is specified,{{ "欢迎使用安企CMS" | trim:"欢迎CMS" }}You will get"使用安企"because it will remove all matching characters from both ends of the string.trimLeftThe filter only removes whitespace or specified characters from the beginning (left side) of a string. For example,{{ " 你好 " | trimLeft }}Will become"你好 "while{{ "前缀-商品" | trimLeft:"前缀-" }}You will get"商品".trimRightThe filter then only removes whitespace or specified characters from the end (right side) of a string. For example,{{ " 你好 " | trimRight }}Will become" 你好"while{{ "商品-后缀" | trimRight:"-后缀" }}You will get"商品".

  2. How do I remove a specific character from the middle of a string?If the goal is to remove a specific character from the middle of a string,cutorreplacethe filter is a more appropriate choice.cutRemove all occurrences of a single character from a string:{{ "He-llo Wor-ld" | cut:"-" }}You will get"Hello World".replaceReplace a specific keyword in a string with another one (or an empty string to remove it):{{ "Hello-World" | replace:"-, " }}You will get"HelloWorld".

  3. replaceCan the filter be used to remove prefixes?AlthoughreplaceThe filter can be used to replace prefixes with an empty string, for example{{ "前缀-内容" | replace:"前缀-," }}. However, this replacement isglobalThis means that if your string also contains the word 'prefix-' in the middle, it will also be replaced. For example,{{ "前缀-内容，这是前缀-说明" | replace:"前缀-," }}You will get"内容，这是说明"Therefore, for removing a specific prefix from the beginning of a string,trimLeftIt is a safer and more accurate choice.