最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
@extend instruction tells Sass that the style of one selector is inherited from another selector.
If one style is almost the same as another, with only a few differences, usethe @extend seems very useful.
In the following Sass example, we created a basic button style Convert the above code to CSS code, as follows: Use .button-basic , then we define two button styles .button-report and .button-submit . They all inherited .button-basic main difference between them is the background color and font color, and all other styles are the same 13.7.1. Sass Code: ¶
.button-basic { border: none; padding: 15px 30px; text-align: center; font-size: 16px; cursor: pointer; } .button-report { @extend .button-basic; background-color: red; } .button-submit { @extend .button-basic; background-color: green; color: white; }
13.7.2. Css Code: ¶
.button-basic, .button-report, .button-submit { border: none; padding: 15px 30px; text-align: center; font-size: 16px; cursor: pointer; } .button-report { background-color: red; } .button-submit { background-color: green; color: white; }
@extend after that, we do not need to specify multiple classes in the HTML button label class="button-basic button-report" , you just need to set the class="button-report" , the class would be fine. @extend reflects the reuse of the code well.