Angular Node.js mysql就像“不喜欢”按钮

Question

我正在为类似Twitter的网站创建YouTube样式（不喜欢）按钮。 但是我在实现喜欢按钮时遇到问题，我在使用Angular Node.js MYSQL，并使用NgFor循环和ngIf条件，我有两个表posts {post_id，user_id，description}和likes {like_id，user_id，post_id，like_status }，具有公用键user_id，post_id。

如果在Likes表中没有特定用户的任何值，我们如何编写条件以显示基本按钮

<div class="container" *ngFor="let post of posts; let i = index ">
   <h6> {{post.description}} </h6>
   <div class="row">          
     <div class="col-md-3">
       <div *ngFor="let like of likes; ">

         <div *ngIf="((post.user_id==like.user_id) && (post.post_id==like.post_id) && (like.like_status=='like'))">
                <button type="button" class="btn btn-success" (click)=likeSubmit(post.user_id,post.post_id)><i class="fa fa-thumbs-up"
                    aria-hidden="true"></i></button>
              </div>

         <div *ngIf="((post.user_id==like.user_id) && (post.post_id==like.post_id) && (like.like_status=='unlike'))">
                <button type="button" class="btn btn-warning" (click)=likeSubmit(post.user_id,post.post_id)><i class="fa fa-thumbs-up"
                    aria-hidden="true"></i></button>
              </div>

<!---problem with ngIf condition -->
       <div *ngIf="ngIf condition">
                <button type="button" class="btn btn-basic" (click)=likeSubmit(post.user_id,post.post_id)><i
                    class="fa fa-thumbs-up" aria-hidden="true"></i></button>
              </div>

前两个ngIf条件运行良好，但我无法为最后一个ngIf条件设置好，如果按钮like_status == like和＆like_status ==与work good不同，如果我们在like表中没有任何值我们可以写ngIf条件o显示按钮

Answer 1

您做的这有点不正确，您不需要在模板中执行内部循环，您可以在组件逻辑中仅执行两个表的联接，然后仅呈现所需的数据。尝试将方法添加到连接两个表的组件中，然后可以轻松地在模板中执行所需的操作。示例：

Ts文件

...
    public getPostsWithLikes() {
        this.posts.map(post => {
            const like = this.likes && this.likes.find(plike => post.user_id === plike.user_id && post.post_id === plike.post_id);
            return {post, like};
        });
    }
...

HTML文件

<div class="container" *ngFor="let item of getPostsWithLikes(); let i = index ">
   <h6> {{item.post.description}} </h6>
   <div class="row">          
     <div class="col-md-3">
         <div *ngIf="item.like && item.like.like_status=='like'">
                <button type="button" class="btn btn-success" (click)=likeSubmit(item.post.user_id,item.post.post_id)><i class="fa fa-thumbs-up"
                    aria-hidden="true"></i></button>
              </div>

         <div *ngIf="item.like && item.like.like_status=='unlike'">
                <button type="button" class="btn btn-warning" (click)=likeSubmit(item.post.user_id,item.post.post_id)><i class="fa fa-thumbs-up"
                    aria-hidden="true"></i></button>
              </div>

<!---if you don't have related record in likes table, like would be null (false), so you just need to invert it-->
       <div *ngIf="!item.like">
                <button type="button" class="btn btn-basic" (click)=likeSubmit(item.post.user_id,item.post.post_id)><i
                    class="fa fa-thumbs-up" aria-hidden="true"></i></button>
              </div>

希望有帮助。