How does the WeChat applet TDesign UI library CSS selector: .t-grid--card take effect?

Detailed explanation of the WeChat applet TDesign UI library CSS selector

When using the WeChat applet TDesign UI library, developers may be confused about the mechanism of action of certain CSS selectors. For example, the class attribute of a page element is t-grid t-card t-class , while the corresponding CSS selector is .t-grid--card . What's going on?

The key to the effectiveness of this selector lies in the external style mechanism of WeChat applets. Instead of applying styles directly, t-class attribute acts as a bridge to dynamically receive style classes from the TDesign UI library. The library uses data binding or other technical means to assign the style class containing .t-grid--card to t-class . Therefore, this selector can take effect even if .t-grid--card is not displayed directly in the DOM structure.

The naming method of .t-grid--card follows the BEM (block), element, modifier) ​​naming convention, aiming to improve the maintainability and readability of CSS. Although it looks like BEM, the TDesign UI library may have simplified it -- here as a modifier, indicating card is a modified state of t-grid . This simplification helps shorten the class name and improves code efficiency.

Finally, it should be emphasized that CSS variables are declared with -- and are used by the var() function. .t-grid--card is not a CSS variable, but a CSS class name that follows the BEM convention.

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