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Route Parameters
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Query Parameters
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<a href="https://github.com/vapor/documentation/blob/master/CONTRIBUTING.md" class="edit">✎ Edit on GitHub</a>
<h1 id="routing-parameters">Routing Parameters</h1>
<p>Traditional web frameworks leave room for error in routing by using strings for route parameter names and types. Vapor takes advantage of Swift's closures to provide a safer and more intuitive method for accessing route parameters.</p>
<h2 id="type-safe">Type Safe</h2>
<p>To create a type safe route simply replace one of the parts of your path with a <code>Type</code>.</p>
<pre><code class="language-swift">drop.get("users", Int.self) { request, userId in
return "You requested User #\(userId)"
}</code></pre>
<p>This creates a route that matches <code>users/:id</code> where the <code>:id</code> is an <code>Int</code>. Here's what it would look like using manual route parameters.</p>
<pre><code class="language-swift">drop.get("users", ":id") { request in
guard let userId = request.parameters["id"]?.int else {
throw Abort.badRequest
}
return "You requested User #\(userId)"
}</code></pre>
<p>Here you can see that type safe routing saves ~3 lines of code and also prevents runtime errors like misspelling <code>:id</code>.</p>
<h2 id="string-initializable">String Initializable</h2>
<p>Any type that conforms to <code>StringInitializable</code> can be used as a type-safe routing parameter. By default, the following types conform:</p>
<ul>
<li>String</li>
<li>Int</li>
<li>Model</li>
</ul>
<p><code>String</code> is the most generic and always matches. <code>Int</code> only matches when the string supplied can be turned into an integer. <code>Model</code> only matches when the string, used as an identifier, can be used to find the model in the database.</p>
<p>Our previous example with users can be further simplified.</p>
<pre><code class="language-swift">drop.get("users", User.self) { request, user in
return "You requested \(user.name)"
}</code></pre>
<p>Here the identifier supplied is automatically used to lookup a user. For example, if <code>/users/5</code> is requested, the <code>User</code> model will be asked for a user with identifier <code>5</code>. If one is found, the request succeeds and the closure is called. If not, a not found error is thrown.</p>
<p>Here is what this would look like if model didn't conform to <code>StringInitializable</code>.</p>
<pre><code class="language-swift">drop.get("users", Int.self) { request, userId in
guard let user = try User.find(userId) else {
throw Abort.notFound
}
return "You requested User #\(userId)"
}</code></pre>
<p>Altogether, type safe routing can save around 6 lines of code from each route.</p>
<h3 id="protocol">Protocol</h3>
<p>Conforming your own types to <code>StringInitializable</code> is easy.</p>
<pre><code class="language-swift">public protocol StringInitializable {
init?(from string: String) throws
}</code></pre>
<p>Here is what <code>Model</code>'s conformance looks like for those who are curious.</p>
<pre><code class="language-swift">extension Model {
public init?(from string: String) throws {
if let model = try Self.find(string) {
self = model
} else {
return nil
}
}
}</code></pre>
<p>The <code>init</code> method can both <code>throw</code> and return <code>nil</code>. This allows you to <code>throw</code> your own errors. Or, if you want the default error and behavior, just return <code>nil</code>.</p>
<h3 id="limits">Limits</h3>
<p>Type safe routing is currently limited to three path parts. This is usually remedied by adding route <a href="group.html">groups</a>.</p>
<pre><code class="language-swift">drop.group("v1", "users") { users in
users.get(User.self, "posts", Post.self) { request, user, post in
return "Requested \(post.name) for \(user.name)"
}
}</code></pre>
<p>The resulting path for the above example is <code>/v1/users/:userId/posts/:postId</code>. If you are clamoring for more type safe routing, please let us know and we can look into increasing the limit of three.</p>
<h2 id="manual">Manual</h2>
<p>As shown briefly above, you are still free to do traditional routing. This can be useful for especially complex situations.</p>
<pre><code class="language-swift">drop.get("v1", "users", ":userId", "posts", ":postId", "comments", ":commentId") { request in
let userId = try request.parameters.extract("userId") as Int
let postId = try request.parameters.extract("postId") as Int
let commentId = try request.parameters.extract("commentId") as Int
return "You requested comment #\(commentId) for post #\(postId) for user #\(userId)"
}</code></pre>
<blockquote>
<p>Property <code>request.parameters</code> is used to extract parameters encoded in the URI <em>path</em> (for example, <code>/v1/users/1</code> has a parameter <code>:userId</code> equal to <code>"1"</code>). In case of parameters passed as a part of a <em>query</em> (e.g. <code>/v1/search-user?userId=1</code>), the <code>request.data</code> should be used (e.g. <code>let userId = request.data["userId"]?.string</code>).</p>
</blockquote>
<p>Request parameters can be accessed either as a dictionary or using the <code>extract</code> syntax which throws instead of returning an optional.</p>
<h3 id="groups">Groups</h3>
<p>Manual request parameters also work with <a href="group.html">groups</a>.</p>
<pre><code class="language-swift">let userGroup = drop.grouped("users", ":userId")
userGroup.get("messages") { req in
let user = try req.parameters.extract("userId") as User
}</code></pre>
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