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POForm binding with custom mapping to object - how?
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copied!<p>I have these case class</p> <pre><code>case class Blog(id:Long, author:User, other stuff...) case class Comment(id:Long, blog:Blog, comment:String) </code></pre> <p>and a form on the client side that submits the data</p> <pre><code>blog_id:"5" comment:"wasssup" </code></pre> <p>I'm writing some simple code to let a user add a comment to a blog.<br> The user is logged in so the his <code>user_id</code> is not needed from the client side, we know who he is... </p> <p>I would like to bind the <code>blog_id</code> to a <code>Blog</code> object loaded from db, and if it doesn't exist show an error.<br> The examples on play framework docs are not helpful.<br> They only show mappings for forms that represent a single Object and all of its fields.<br> Here I'm representing a tuple of a <code>(b:Blog, comment:String)</code> and for the <code>Blog</code> I'm only supplying it's <code>id</code>. </p> <p>I'd like to have a mapping that would provide me with the <strong>conversion + validation + error messages</strong>, so i can write something like: </p> <pre><code>val form = Form( tuple( "blog_id" -> blogMapping, "comment" -> nonEmptyText ) ) form.bindFromRequest().fold(... formWithErrors => {... }, { case (blog, comment) => {do some db stuff to create the comment} ... </code></pre> <p>The "blogMapping" wlil work like other mappings, it will bind the posted data to an object, in our case a blog loaded from db, and in case it's not successful it will provide an error that we can use on the <code>formWithErrors =></code> clause.</p> <p>I'm not sure how to accomplish this, the docs are kinda lacking here...<br> any help is appreciated!</p>

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