Question

我在“ db”中具有关键字“：questions”的这种结构（有序映射）：

{:33 {:question "one", :id 33, :answers [{:id 22, :question_id 33, :answer "one", :correct false}
                                              {:id 4,  :question_id 33, :answer "two", :correct false}]}},
{:39 {:question "two", :id 39, :answers []}},
{:41 {:question "three", :id 41, :answers [{:id 29, :question_id 41, :answer "one", :correct false}
                                                {:id 35, :question_id 41, :answer "two", :correct true}]}}

我可以在事件处理程序“ re-frame / reg-event-db”中添加一个新问题，并添加：

(assoc-in db [:questions (:id response)] new-map-stuff)

但是我不知道如何在“：answers”键中添加地图。此外，我担心每次添加新答案时都会渲染所有问题。

我阅读了有关“路径”拦截器（种类为“ update-in”）的信息，但找不到有关如何使用它的示例。

Answer 1

您可以像使用普通intent?.extras?.getString(ARG_TEMPLATE_CODE)一样简单地进行此操作。首先从Clojure CheatSheet开始：

http://jafingerhut.github.io/cheatsheet/clojuredocs/cheatsheet-tiptip-cdocs-summary.html

或ClojureScript版本：http://cljs.info

查看update-in的文档：https://clojuredocs.org/clojure.core/update-in

您需要2个组件

导航突变位点的路径
从（1）点开始执行突变的功能。

您没有完全指定数据。我假设它看起来像这样：

update-in

我将组成一个新的(def db {:questions [ {:33 {:question "one", :id 33, :answers [{:id 22, :question_id 33, :answer "one", :correct false} {:id 4, :question_id 33, :answer "two", :correct false}]}}, {:39 {:question "two", :id 39, :answers []}}, {:41 {:question "three", :id 41, :answers [{:id 29, :question_id 41, :answer "one", :correct false} {:id 35, :question_id 41, :answer "two", :correct true}]}}]})地图以添加：

answer

此代码分步显示了该过程。

(def new-answer {:id 42, :question_id 442, :answer "The Ultimate", :correct false})

首先导航以获取(let [submap (get-in db [:questions 0 :33 :answers]) modified (conj submap new-answer) final-answer (update-in db [:questions 0 :33 :answers] conj new-answer) ]：

submap

添加新答案的方式：

submap => 
[{:id 22, :question_id 33, :answer "one", :correct false}
 {:id  4, :question_id 33, :answer "two", :correct false}]

将所有内容放在一起进行一次操作：

modified => 
[{:id 22, :question_id  33, :answer "one", :correct false}
 {:id  4, :question_id  33, :answer "two", :correct false}
 {:id 42, :question_id 442, :answer "The Ultimate", :correct false}]

所有这些在ClojureScript中的工作方式与Clojure中的相同。

不用担心使用final-answer => {:questions [{:33 {:question "one", :id 33, :answers [{:id 22, :question_id 33, :answer "one", :correct false} {:id 4, :question_id 33, :answer "two", :correct false} {:id 42, :question_id 442, :answer "The Ultimate", :correct false}]}} {:39 {:question "two", :id 39, :answers []}} {:41 {:question "three", :id 41, :answers [{:id 29, :question_id 41, :answer "one", :correct false} {:id 35, :question_id 41, :answer "two", :correct true}]}}]}拦截器。我认为它使事情变得混乱多于帮助。除非以下条件，否则不必担心渲染速度：

您已经对其进行了测试并知道它是正确的。
您已经测量了渲染速度，并可以记录问题和需要加快的速度。
要获取长列表，请查看path元数据，您可以将其添加到Reagent的每个列表元素中。参见：Reagent React Clojurescript Warning: Every element in a seq should have a unique :key

更新

请注意， 仅出于演示目的而显示key和submap ，以展示modified的工作原理。 update-in表达式是您实际要包含在代码中的唯一内容。另外，请注意，update-in 仅使用 update-in和db。

重新构图：在嵌套向量中添加新的地图元素

1 个答案: