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<ol class="chapter"><li class="chapter-item expanded "><a href="../intro.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="../CONTRIBUTING.html"><strong aria-hidden="true">2.</strong> Contributing</a></li><li class="chapter-item expanded "><a href="../idioms/index.html"><strong aria-hidden="true">3.</strong> Idioms</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../idioms/coercion-arguments.html"><strong aria-hidden="true">3.1.</strong> Use borrowed types for arguments</a></li><li class="chapter-item expanded "><a href="../idioms/concat-format.html" class="active"><strong aria-hidden="true">3.2.</strong> Concatenating Strings with format!</a></li><li class="chapter-item expanded "><a href="../idioms/ctor.html"><strong aria-hidden="true">3.3.</strong> Constructor</a></li><li class="chapter-item expanded "><a href="../idioms/default.html"><strong aria-hidden="true">3.4.</strong> The Default 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href="../idioms/ffi-accepting-strings.html"><strong aria-hidden="true">3.9.2.</strong> Accepting Strings</a></li><li class="chapter-item expanded "><a href="../idioms/ffi-passing-strings.html"><strong aria-hidden="true">3.9.3.</strong> Passing Strings</a></li></ol></li><li class="chapter-item expanded "><a href="../idioms/option-iter.html"><strong aria-hidden="true">3.10.</strong> Iterating over an Option</a></li><li class="chapter-item expanded "><a href="../idioms/pass-var-to-closure.html"><strong aria-hidden="true">3.11.</strong> Pass Variables to Closure</a></li><li class="chapter-item expanded "><a href="../idioms/priv-extend.html"><strong aria-hidden="true">3.12.</strong> Privacy For Extensibility</a></li><li class="chapter-item expanded "><a href="../idioms/rustdoc-init.html"><strong aria-hidden="true">3.13.</strong> Easy doc initialization</a></li><li class="chapter-item expanded "><a href="../idioms/temporary-mutability.html"><strong aria-hidden="true">3.14.</strong> Temporary mutability</a></li></ol></li><li class="chapter-item expanded "><a href="../patterns/index.html"><strong aria-hidden="true">4.</strong> Design Patterns</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../patterns/builder.html"><strong aria-hidden="true">4.1.</strong> Builder</a></li><li class="chapter-item expanded "><a href="../patterns/compose-structs.html"><strong aria-hidden="true">4.2.</strong> Compose Structs</a></li><li class="chapter-item expanded "><a href="../patterns/entry.html"><strong aria-hidden="true">4.3.</strong> Entry API</a></li><li class="chapter-item expanded "><a href="../patterns/ffi-intro.html"><strong aria-hidden="true">4.4.</strong> Foreign function interface usage</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../patterns/ffi-export.html"><strong aria-hidden="true">4.4.1.</strong> Object-Based APIs</a></li><li class="chapter-item expanded "><a href="../patterns/ffi-wrappers.html"><strong aria-hidden="true">4.4.2.</strong> Type Consolidation into Wrappers</a></li></ol></li><li class="chapter-item expanded "><a href="../patterns/fold.html"><strong aria-hidden="true">4.5.</strong> Fold</a></li><li class="chapter-item expanded "><a href="../patterns/newtype.html"><strong aria-hidden="true">4.6.</strong> Newtype</a></li><li class="chapter-item expanded "><a href="../patterns/RAII.html"><strong aria-hidden="true">4.7.</strong> RAII Guards</a></li><li class="chapter-item expanded "><a href="../patterns/small-crates.html"><strong aria-hidden="true">4.8.</strong> Prefer Small Crates</a></li><li class="chapter-item expanded "><a href="../patterns/unsafe-mods.html"><strong aria-hidden="true">4.9.</strong> Contain unsafety in small modules</a></li><li class="chapter-item expanded "><a href="../patterns/visitor.html"><strong aria-hidden="true">4.10.</strong> Visitor</a></li></ol></li><li class="chapter-item expanded "><a href="../anti_patterns/index.html"><strong 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<h1><a class="header" href="#concatenating-strings-with-format" id="concatenating-strings-with-format">Concatenating strings with <code>format!</code></a></h1>
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<h2><a class="header" href="#description" id="description">Description</a></h2>
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<p>It is possible to build up strings using the <code>push</code> and <code>push_str</code> methods on a
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mutable <code>String</code>, or using its <code>+</code> operator. However, it is often more
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convenient to use <code>format!</code>, especially where there is a mix of literal and
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non-literal strings.</p>
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<h2><a class="header" href="#example" id="example">Example</a></h2>
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<pre><pre class="playground"><code class="language-rust edition2018">
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<span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>fn say_hello(name: &str) -> String {
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// We could construct the result string manually.
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// let mut result = "Hello ".to_owned();
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// result.push_str(name);
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// result.push('!');
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// result
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// But using format! is better.
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format!("Hello {}!", name)
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}
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<span class="boring">}
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</span></code></pre></pre>
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<h2><a class="header" href="#advantages" id="advantages">Advantages</a></h2>
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<p>Using <code>format!</code> is usually the most succinct and readable way to combine strings.</p>
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<h2><a class="header" href="#disadvantages" id="disadvantages">Disadvantages</a></h2>
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<p>It is usually not the most efficient way to combine strings - a series of <code>push</code>
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operations on a mutable string is usually the most efficient (especially if the
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string has been pre-allocated to the expected size).</p>
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