angular.js - angularjs directive 中 scope '=?' 表达的是什么意思？

Question

angularjs directive 中 scope '=?' 表达的是什么意思？

Answer 1

If the parent scope property doesn't exist, it will throw a NON_ASSIGNABLE_MODEL_EXPRESSION exception. You can avoid this behavior using =? or =?attr in order to flag the property as optional.

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If you want to shallow watch for changes (i.e. $watchCollection instead of $watch) you can use =* or =*attr (=*? or =*?attr if the property is optional).

Answer 2

双向的数据绑定，你可以看看这里传送门