ERROR Error: dataKey must be defined to use row expansion - html

Question

I'm trying to figure out how to use Row Expansion in PrimeEng. I was just following the guide in their documentation and it shows that I should define my datakey. I already defined it below if I'm not mistaken. I'm new to this, please don't judge.
<p-table [value]="users" [paginator]="true" [rows]="10" [showCurrentPageReport]="true"
currentPageReportTemplate="Showing {first} to {last} of {totalRecords} entries"
[rowsPerPageOptions]="[10, 25, 50]">
<ng-template pTemplate="header">
<tr>
<th style="width:2rem">blank</th>
<th style="width:1rem">ID</th>
<th style="width:8rem">Name</th>
<th style="width:8rem">Username</th>
<th style="width:8rem">Email</th>
<th style="width:8rem">Street</th>
<th style="width:8rem">Suite</th>
<th style="width:8rem">City</th>
<th style="width:8rem">Zip code</th>
<th style="width:8rem">LAT</th>
<th style="width:8rem">LNG</th>
<th style="width:8rem">Phone</th>
<th style="width:8rem">Website</th>
</tr>
</ng-template>
<ng-template pTemplate="body" let-user let-expanded="expanded">
<tr>
<td>
<!-- <button type="button" pButton pRipple (click)="viewPostUser(user.id)" class="p-button-text p-button-rounded p-button-plain" ></button> -->
<button type="button" pButton pRipple [pRowToggler]="posts" (click)="viewPostUser(user.id)" class="p-button-text p-button-rounded p-button-plain" [icon]="expanded ? 'pi pi-chevron-down' : 'pi pi-chevron-right'"></button>
</td>
<td>{{user.id}}</td>
<td>{{user.name}}</td>
<td>{{user.username}}</td>
<td>{{user.email}}</td>
<td>{{user.address.street}}</td>
<td>{{user.address.suite}}</td>
<td>{{user.address.city}}</td>
<td>{{user.address.zipcode}}</td>
<td>{{user.address.geo.lat}}</td>
<td>{{user.address.geo.lng}}</td>
<td>{{user.phone}}</td>
<td>{{user.website}}</td>
</tr>
</ng-template>
Here is my row expansion ng-template.
<ng-template pTemplate="rowexpansion" let-posts>
<tr>
<td colspan="7">
<div class="p-p-3">
<p-table [value]="posts.userId" [dataKey]="posts.userId">
<ng-template pTemplate="header">
<tr>
<th style="width:4rem">userID</th>
<th style="width:4rem">ID</th>
<th style="width:4rem">Title</th>
<th style="width:4rem">Body</th>
</tr>
</ng-template>
<ng-template pTemplate="body" let-posts>
<tr>
<td>{{posts.userId}}</td>
<td>{{posts.id}}</td>
<td>{{posts.title}}</td>
<td>{{posts.body}}</td>
<td><p-button type="button" icon="pi pi-search"></p-button></td>
</tr>
</ng-template>
</p-table>
</div>
</td>
</tr>
</ng-template>
I've tried searching the error that I have, but it points me to updating the version.

Answer 1

I think here is where you get it wrong:
[value]="posts.userId" [dataKey]="posts.userId"
[value] is the collection that you want to iterate through, which should be posts in this case
[dataKey] is the property of one item in that collection which you could just define by name: userId
So the final code is:
[value]="posts" [dataKey]="userId"

Answer 2

First, to fix the error you're seeing, add the attribute dataKey="id" to the p-table element.
Next, using let-posts is probably not what you wanted. You didn't write how your data structure is constructed but I'll assume each user has a property called posts. You need to change your template like this:
<ng-template pTemplate="rowexpansion" let-user>
<tr>
<td colspan="7">
<div class="p-p-3">
<p-table [value]="user.posts" dataKey="id">
<ng-template pTemplate="header">
<tr>
<th style="width:4rem">userID</th>
<th style="width:4rem">ID</th>
<th style="width:4rem">Title</th>
<th style="width:4rem">Body</th>
</tr>
</ng-template>
<ng-template pTemplate="body" let-post>
<tr>
<td>{{post.userId}}</td>
<td>{{post.id}}</td>
<td>{{post.title}}</td>
<td>{{post.body}}</td>
<td><p-button type="button" icon="pi pi-search"></p-button></td>
</tr>
</ng-template>
</p-table>
</div>
</td>
</tr>
</ng-template>
Explanation:
Use let-user in the rowexpansion template. Now the user variable will contain the user data for the current expandable row.
In the inner p-table, provide the [value] input with the data for the sub table, i.e., the posts for the current user.
In the inner p-table, provide the dataKey input with the name of the field which is the unique key of the table. This might be even not necessary in your case.
In the inner p-table, in the body template, use let-post instead of let-posts since each iteration, i.e., each row of the inner table showing posts for the user, will store the current row, which is a single post.
In each <td> element in the inner table's body template, use post.<field-name>. post will contain the data for the current row so all you need to do is access the field you need inside the object.

Answer 3

You can add dataKey in first line, like this
<p-table [value]="users" dataKey="name">
Maybe it will solve your problem.