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Joshua Holmer 56e0e2de01 Add interface for rustdoc to github pages 
Closes #28
2016-03-11 12:13:13 -05:00

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<h1 class='fqn'><span class='in-band'><a href='index.html'>clap</a>::<wbr><a class='macro' href=''>value_t!</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a id='src-4574' class='srclink' href='../src/clap/macros.rs.html.html#174-208' title='goto source code'>[src]</a></span></h1>
<pre class='rust macro'>
<span class='macro'>macro_rules</span><span class='macro'>!</span> <span class='ident'>value_t</span> {
(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>m</span>:<span class='ident'>ident</span>.<span class='ident'>value_of</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>v</span>:<span class='ident'>expr</span>), <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>t</span>:<span class='ident'>ty</span>) <span class='op'>=&gt;</span> { ... };
(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>m</span>:<span class='ident'>ident</span>.<span class='ident'>values_of</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>v</span>:<span class='ident'>expr</span>), <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>t</span>:<span class='ident'>ty</span>) <span class='op'>=&gt;</span> { ... };
}</pre>
<div class='docblock'><p>Convenience macro getting a typed value <code>T</code> where <code>T</code> implements <code>std::str::FromStr</code>
This macro returns a <code>Result&lt;T,String&gt;</code> which allows you as the developer to decide
what you&#39;d like to do on a failed parse. There are two types of errors, parse failures
and those where the argument wasn&#39;t present (such as a non-required argument).</p>
<p>You can use it to get a single value, or a <code>Vec&lt;T&gt;</code> with the <code>values_of()</code></p>
<p><strong>NOTE:</strong> Be cautious, as since this a macro invocation it&#39;s not exactly like
standard syntax.</p>
<h1 id='examples-single-value' class='section-header'><a href='#examples-single-value'>Examples single value</a></h1>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>matches</span> <span class='op'>=</span> <span class='ident'>App</span>::<span class='ident'>new</span>(<span class='string'>&quot;myapp&quot;</span>)
.<span class='ident'>arg_from_usage</span>(<span class='string'>&quot;[length] &#39;Set the length to use as a pos whole num, i.e. 20&#39;&quot;</span>)
.<span class='ident'>get_matches</span>();
<span class='kw'>let</span> <span class='ident'>len</span> <span class='op'>=</span> <span class='macro'>value_t</span><span class='macro'>!</span>(<span class='ident'>matches</span>.<span class='ident'>value_of</span>(<span class='string'>&quot;length&quot;</span>), <span class='ident'>u32</span>)
.<span class='ident'>unwrap_or_else</span>(<span class='op'>|</span><span class='ident'>e</span><span class='op'>|</span>{
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;{}&quot;</span>,<span class='ident'>e</span>);
<span class='ident'>std</span>::<span class='ident'>process</span>::<span class='ident'>exit</span>(<span class='number'>1</span>)
});
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;{} + 2: {}&quot;</span>, <span class='ident'>len</span>, <span class='ident'>len</span> <span class='op'>+</span> <span class='number'>2</span>);</pre>
<h1 id='examples-multiple-values' class='section-header'><a href='#examples-multiple-values'>Examples multiple values</a></h1>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>matches</span> <span class='op'>=</span> <span class='ident'>App</span>::<span class='ident'>new</span>(<span class='string'>&quot;myapp&quot;</span>)
.<span class='ident'>arg_from_usage</span>(<span class='string'>&quot;[seq]... &#39;A sequence of pos whole nums, i.e. 20 45&#39;&quot;</span>)
.<span class='ident'>get_matches</span>();
<span class='kw'>for</span> <span class='ident'>v</span> <span class='kw'>in</span> <span class='macro'>value_t</span><span class='macro'>!</span>(<span class='ident'>matches</span>.<span class='ident'>values_of</span>(<span class='string'>&quot;seq&quot;</span>), <span class='ident'>u32</span>)
.<span class='ident'>unwrap_or_else</span>(<span class='op'>|</span><span class='ident'>e</span><span class='op'>|</span>{
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;{}&quot;</span>,<span class='ident'>e</span>);
<span class='ident'>std</span>::<span class='ident'>process</span>::<span class='ident'>exit</span>(<span class='number'>1</span>)
}) {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;{} + 2: {}&quot;</span>, <span class='ident'>v</span>, <span class='ident'>v</span> <span class='op'>+</span> <span class='number'>2</span>);
}</pre>
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