summaryrefslogtreecommitdiffstats
path: root/docs/en/cowboy/2.0/guide/constraints
diff options
context:
space:
mode:
Diffstat (limited to 'docs/en/cowboy/2.0/guide/constraints')
-rw-r--r--docs/en/cowboy/2.0/guide/constraints/index.html275
1 files changed, 139 insertions, 136 deletions
diff --git a/docs/en/cowboy/2.0/guide/constraints/index.html b/docs/en/cowboy/2.0/guide/constraints/index.html
index 110adf07..570f49fe 100644
--- a/docs/en/cowboy/2.0/guide/constraints/index.html
+++ b/docs/en/cowboy/2.0/guide/constraints/index.html
@@ -7,7 +7,7 @@
<meta name="description" content="">
<meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara">
- <meta name="generator" content="Hugo 0.17" />
+ <meta name="generator" content="Hugo 0.26" />
<title>Nine Nines: Constraints</title>
@@ -67,147 +67,150 @@
<h1 class="lined-header"><span>Constraints</span></h1>
-<div class="paragraph"><p>Constraints are validation and conversion functions applied
-to user input.</p></div>
-<div class="paragraph"><p>They are used in various places in Cowboy, including the
-router and the <code>cowboy_req</code> match functions.</p></div>
-<div class="sect1">
-<h2 id="_syntax">Syntax</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Constraints are provided as a list of fields. For each field
-in the list, specific constraints can be applied, as well as
-a default value if the field is missing.</p></div>
-<div class="paragraph"><p>A field can take the form of an atom <code>field</code>, a tuple with
-constraints <code>{field, Constraints}</code> or a tuple with constraints
-and a default value <code>{field, Constraints, Default}</code>.
-The <code>field</code> form indicates the field is mandatory.</p></div>
-<div class="paragraph"><p>Note that when used with the router, only the second form
-makes sense, as it does not use the default and the field
-is always defined.</p></div>
-<div class="paragraph"><p>Constraints for each field are provided as an ordered list
-of atoms or funs to apply. Built-in constraints are provided
-as atoms, while custom constraints are provided as funs.</p></div>
-<div class="paragraph"><p>When multiple constraints are provided, they are applied in
-the order given. If the value has been modified by a constraint
-then the next one receives the new value.</p></div>
-<div class="paragraph"><p>For example, the following constraints will first validate
-and convert the field <code>my_value</code> to an integer, and then
-check that the integer is positive:</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="color: #009900">PositiveFun</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span>
- (<span style="color: #990000">_</span>, <span style="color: #009900">V</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">V</span> <span style="color: #990000">&gt;</span> <span style="color: #993399">0</span> <span style="color: #990000">-&gt;</span>
- {<span style="color: #FF6600">ok</span>, <span style="color: #009900">V</span>};
- (<span style="color: #990000">_</span>, <span style="color: #990000">_</span>) <span style="color: #990000">-&gt;</span>
- {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">not_positive</span>}
-<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
-{<span style="color: #FF6600">my_value</span>, [<span style="color: #FF6600">int</span>, <span style="color: #009900">PositiveFun</span>]}<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>We ignore the first fun argument in this snippet. We shouldn&#8217;t.
-We will simply learn what it is later in this chapter.</p></div>
-<div class="paragraph"><p>When there&#8217;s only one constraint, it can be provided directly
-without wrapping it into a list:</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt>{<span style="color: #FF6600">my_value</span>, <span style="color: #FF6600">int</span>}</tt></pre></div></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_built_in_constraints">Built-in constraints</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Built-in constraints are specified as an atom:</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="border"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="top"> Constraint </th>
-<th align="left" valign="top"> Description</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="top"><p class="table">int</p></td>
-<td align="left" valign="top"><p class="table">Converts binary value to integer.</p></td>
-</tr>
-<tr>
-<td align="left" valign="top"><p class="table">nonempty</p></td>
-<td align="left" valign="top"><p class="table">Ensures the binary value is non-empty.</p></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_custom_constraints">Custom constraints</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Custom constraints are specified as a fun. This fun takes
-two arguments. The first argument indicates the operation
-to be performed, and the second is the value. What the
-value is and what must be returned depends on the operation.</p></div>
-<div class="paragraph"><p>Cowboy currently defines three operations. The operation
-used for validating and converting user input is the <code>forward</code>
-operation.</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="font-weight: bold"><span style="color: #000000">int</span></span>(<span style="color: #FF6600">forward</span>, <span style="color: #009900">Value</span>) <span style="color: #990000">-&gt;</span>
- <span style="font-weight: bold"><span style="color: #0000FF">try</span></span>
- {<span style="color: #FF6600">ok</span>, <span style="font-weight: bold"><span style="color: #000000">binary_to_integer</span></span>(<span style="color: #009900">Value</span>)}
- <span style="font-weight: bold"><span style="color: #0000FF">catch</span></span> <span style="color: #990000">_:_</span> <span style="color: #990000">-&gt;</span>
- {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">not_an_integer</span>}
- <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>;</tt></pre></div></div>
-<div class="paragraph"><p>The value must be returned even if it is not converted
-by the constraint.</p></div>
-<div class="paragraph"><p>The <code>reverse</code> operation does the opposite: it
-takes a converted value and changes it back to what the
-user input would have been.</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="font-weight: bold"><span style="color: #000000">int</span></span>(<span style="color: #FF6600">reverse</span>, <span style="color: #009900">Value</span>) <span style="color: #990000">-&gt;</span>
- <span style="font-weight: bold"><span style="color: #0000FF">try</span></span>
- {<span style="color: #FF6600">ok</span>, <span style="font-weight: bold"><span style="color: #000000">integer_to_binary</span></span>(<span style="color: #009900">Value</span>)}
- <span style="font-weight: bold"><span style="color: #0000FF">catch</span></span> <span style="color: #990000">_:_</span> <span style="color: #990000">-&gt;</span>
- {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">not_an_integer</span>}
- <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>;</tt></pre></div></div>
-<div class="paragraph"><p>Finally, the <code>format_error</code> operation takes an error
-returned by any other operation and returns a formatted
-human-readable error message.</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="font-weight: bold"><span style="color: #000000">int</span></span>(<span style="color: #FF6600">format_error</span>, {<span style="color: #FF6600">not_an_integer</span>, <span style="color: #009900">Value</span>}) <span style="color: #990000">-&gt;</span>
- <span style="font-weight: bold"><span style="color: #000000">io_lib:format</span></span>(<span style="color: #FF0000">"The value ~p is not an integer."</span>, [<span style="color: #009900">Value</span>])<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Notice that for this case you get both the error and
-the value that was given to the constraint that produced
-this error.</p></div>
-<div class="paragraph"><p>Cowboy will not catch exceptions coming from constraint
-functions. They should be written to not emit any exceptions.</p></div>
-</div>
-</div>
+<div class="paragraph"><p>Constraints are validation and conversion functions applied
+to user input.</p></div>
+<div class="paragraph"><p>They are used in various places in Cowboy, including the
+router and the <code>cowboy_req</code> match functions.</p></div>
+<div class="sect1">
+<h2 id="_syntax">Syntax</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Constraints are provided as a list of fields. For each field
+in the list, specific constraints can be applied, as well as
+a default value if the field is missing.</p></div>
+<div class="paragraph"><p>A field can take the form of an atom <code>field</code>, a tuple with
+constraints <code>{field, Constraints}</code> or a tuple with constraints
+and a default value <code>{field, Constraints, Default}</code>.
+The <code>field</code> form indicates the field is mandatory.</p></div>
+<div class="paragraph"><p>Note that when used with the router, only the second form
+makes sense, as it does not use the default and the field
+is always defined.</p></div>
+<div class="paragraph"><p>Constraints for each field are provided as an ordered list
+of atoms or funs to apply. Built-in constraints are provided
+as atoms, while custom constraints are provided as funs.</p></div>
+<div class="paragraph"><p>When multiple constraints are provided, they are applied in
+the order given. If the value has been modified by a constraint
+then the next one receives the new value.</p></div>
+<div class="paragraph"><p>For example, the following constraints will first validate
+and convert the field <code>my_value</code> to an integer, and then
+check that the integer is positive:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">PositiveFun</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span>
+ (<span style="color: #990000">_</span>, <span style="color: #009900">V</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">V</span> <span style="color: #990000">&gt;</span> <span style="color: #993399">0</span> <span style="color: #990000">-&gt;</span>
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">V</span>};
+ (<span style="color: #990000">_</span>, <span style="color: #990000">_</span>) <span style="color: #990000">-&gt;</span>
+ {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">not_positive</span>}
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
+{<span style="color: #FF6600">my_value</span>, [<span style="color: #FF6600">int</span>, <span style="color: #009900">PositiveFun</span>]}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>We ignore the first fun argument in this snippet. We shouldn&#8217;t.
+We will simply learn what it is later in this chapter.</p></div>
+<div class="paragraph"><p>When there&#8217;s only one constraint, it can be provided directly
+without wrapping it into a list:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">my_value</span>, <span style="color: #FF6600">int</span>}</tt></pre></div></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_built_in_constraints">Built-in constraints</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Built-in constraints are specified as an atom:</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="border"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="top"> Constraint </th>
+<th align="left" valign="top"> Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="top"><p class="table">int</p></td>
+<td align="left" valign="top"><p class="table">Converts binary value to integer.</p></td>
+</tr>
+<tr>
+<td align="left" valign="top"><p class="table">nonempty</p></td>
+<td align="left" valign="top"><p class="table">Ensures the binary value is non-empty.</p></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_custom_constraints">Custom constraints</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Custom constraints are specified as a fun. This fun takes
+two arguments. The first argument indicates the operation
+to be performed, and the second is the value. What the
+value is and what must be returned depends on the operation.</p></div>
+<div class="paragraph"><p>Cowboy currently defines three operations. The operation
+used for validating and converting user input is the <code>forward</code>
+operation.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">int</span></span>(<span style="color: #FF6600">forward</span>, <span style="color: #009900">Value</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">try</span></span>
+ {<span style="color: #FF6600">ok</span>, <span style="font-weight: bold"><span style="color: #000000">binary_to_integer</span></span>(<span style="color: #009900">Value</span>)}
+ <span style="font-weight: bold"><span style="color: #0000FF">catch</span></span> <span style="color: #990000">_:_</span> <span style="color: #990000">-&gt;</span>
+ {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">not_an_integer</span>}
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>;</tt></pre></div></div>
+<div class="paragraph"><p>The value must be returned even if it is not converted
+by the constraint.</p></div>
+<div class="paragraph"><p>The <code>reverse</code> operation does the opposite: it
+takes a converted value and changes it back to what the
+user input would have been.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">int</span></span>(<span style="color: #FF6600">reverse</span>, <span style="color: #009900">Value</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">try</span></span>
+ {<span style="color: #FF6600">ok</span>, <span style="font-weight: bold"><span style="color: #000000">integer_to_binary</span></span>(<span style="color: #009900">Value</span>)}
+ <span style="font-weight: bold"><span style="color: #0000FF">catch</span></span> <span style="color: #990000">_:_</span> <span style="color: #990000">-&gt;</span>
+ {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">not_an_integer</span>}
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>;</tt></pre></div></div>
+<div class="paragraph"><p>Finally, the <code>format_error</code> operation takes an error
+returned by any other operation and returns a formatted
+human-readable error message.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">int</span></span>(<span style="color: #FF6600">format_error</span>, {<span style="color: #FF6600">not_an_integer</span>, <span style="color: #009900">Value</span>}) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000000">io_lib:format</span></span>(<span style="color: #FF0000">"The value ~p is not an integer."</span>, [<span style="color: #009900">Value</span>])<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Notice that for this case you get both the error and
+the value that was given to the constraint that produced
+this error.</p></div>
+<div class="paragraph"><p>Cowboy will not catch exceptions coming from constraint
+functions. They should be written to not emit any exceptions.</p></div>
+</div>
+</div>
+
+
+
<nav style="margin:1em 0">
generated by cgit v1.2.3 (git 2.25.1) at 2025-04-26 20:32:21 +0000