flatbuffers_guide_use_go.html - third_party/flatbuffers - Git at Google

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 <div class="PageDoc"><div class="header">
   <div class="headertitle">
 <div class="title">Use in Go </div>  </div>
 </div><!--header-->
 <div class="contents">
 <div class="textblock"><p><a class="anchor" id="md_GoUsage"></a></p>
 <h1><a class="anchor" id="autotoc_md77"></a>
 Before you get started</h1>
 <p>Before diving into the FlatBuffers usage in Go, it should be noted that the <a class="el" href="flatbuffers_guide_tutorial.html">Tutorial</a> page has a complete guide to general FlatBuffers usage in all of the supported languages (including Go). This page is designed to cover the nuances of FlatBuffers usage, specific to Go.</p>
 <p>You should also have read the <a class="el" href="flatbuffers_guide_building.html">Building</a> documentation to build <code>flatc</code> and should be familiar with <a class="el" href="flatbuffers_guide_using_schema_compiler.html">Using the schema compiler</a> and <a class="el" href="flatbuffers_guide_writing_schema.html">Writing a schema</a>.</p>
 <h1><a class="anchor" id="autotoc_md78"></a>
 FlatBuffers Go library code location</h1>
 <p>The code for the FlatBuffers Go library can be found at <code>flatbuffers/go</code>. You can browse the library code on the <a href="https://github.com/google/flatbuffers/tree/master/go">FlatBuffers GitHub page</a>.</p>
 <h1><a class="anchor" id="autotoc_md79"></a>
 Testing the FlatBuffers Go library</h1>
 <p>The code to test the Go library can be found at <code>flatbuffers/tests</code>. The test code itself is located in <a href="https://github.com/google/
 flatbuffers/blob/master/tests/go_test.go">go_test.go</a>.</p>
 <p>To run the tests, use the <a href="https://github.com/google/flatbuffers/
 blob/master/tests/GoTest.sh">GoTest.sh</a> shell script.</p>
 <p><em>Note: The shell script requires <a href="https://golang.org/doc/install">Go</a> to be installed.</em></p>
 <h1><a class="anchor" id="autotoc_md80"></a>
 Using the FlatBuffers Go library</h1>
 <p><em>Note: See <a class="el" href="flatbuffers_guide_tutorial.html">Tutorial</a> for a more in-depth example of how to use FlatBuffers in Go.</em></p>
 <p>FlatBuffers supports reading and writing binary FlatBuffers in Go.</p>
 <p>To use FlatBuffers in your own code, first generate Go classes from your schema with the <code>--go</code> option to <code>flatc</code>. Then you can include both FlatBuffers and the generated code to read or write a FlatBuffer.</p>
 <p>For example, here is how you would read a FlatBuffer binary file in Go: First, include the library and generated code. Then read a FlatBuffer binary file into a <code>[]byte</code>, which you pass to the <code>GetRootAsMonster</code> function:</p>
 <div class="fragment"><div class="line">import (</div>
 <div class="line">   example &quot;MyGame/Example&quot;</div>
 <div class="line">   flatbuffers &quot;github.com/google/flatbuffers/go&quot;</div>
 <div class="line"> </div>
 <div class="line">   io/ioutil</div>
 <div class="line">)</div>
 <div class="line"> </div>
 <div class="line">buf, err := ioutil.ReadFile(&quot;monster.dat&quot;)</div>
 <div class="line">// handle err</div>
 <div class="line">monster := example.GetRootAsMonster(buf, 0)</div>
 </div><!-- fragment --><p>Now you can access values like this:</p>
 <div class="fragment"><div class="line">hp := monster.Hp()</div>
 <div class="line">pos := monster.Pos(nil)</div>
 </div><!-- fragment --><p>In some cases it's necessary to modify values in an existing FlatBuffer in place (without creating a copy). For this reason, scalar fields of a Flatbuffer table or struct can be mutated.</p>
 <div class="fragment"><div class="line">monster := example.GetRootAsMonster(buf, 0)</div>
 <div class="line"> </div>
 <div class="line">// Set table field.</div>
 <div class="line">if ok := monster.MutateHp(10); !ok {</div>
 <div class="line">  panic(&quot;failed to mutate Hp&quot;)</div>
 <div class="line">}</div>
 <div class="line"> </div>
 <div class="line">// Set struct field.</div>
 <div class="line">monster.Pos().MutateZ(4)</div>
 <div class="line"> </div>
 <div class="line">// This mutation will fail because the mana field is not available in</div>
 <div class="line">// the buffer. It should be set when creating the buffer.</div>
 <div class="line">if ok := monster.MutateMana(20); !ok {</div>
 <div class="line">  panic(&quot;failed to mutate Hp&quot;)</div>
 <div class="line">}</div>
 </div><!-- fragment --><p>The term <code>mutate</code> is used instead of <code>set</code> to indicate that this is a special use case. All mutate functions return a boolean value which is false if the field we're trying to mutate is not available in the buffer.</p>
 <h1><a class="anchor" id="autotoc_md81"></a>
 Text Parsing</h1>
 <p>There currently is no support for parsing text (Schema's and JSON) directly from Go, though you could use the C++ parser through cgo. Please see the C++ documentation for more on text parsing.</p>
 <p><br  />
  </p>
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	<div class="PageDoc"><div class="header">
	<div class="headertitle">
	<div class="title">Use in Go </div> </div>
	</div><!--header-->
	<div class="contents">
	<div class="textblock"><p><a class="anchor" id="md_GoUsage"></a></p>
	<h1><a class="anchor" id="autotoc_md77"></a>
	Before you get started</h1>
	<p>Before diving into the FlatBuffers usage in Go, it should be noted that the <a class="el" href="flatbuffers_guide_tutorial.html">Tutorial</a> page has a complete guide to general FlatBuffers usage in all of the supported languages (including Go). This page is designed to cover the nuances of FlatBuffers usage, specific to Go.</p>
	<p>You should also have read the <a class="el" href="flatbuffers_guide_building.html">Building</a> documentation to build <code>flatc</code> and should be familiar with <a class="el" href="flatbuffers_guide_using_schema_compiler.html">Using the schema compiler</a> and <a class="el" href="flatbuffers_guide_writing_schema.html">Writing a schema</a>.</p>
	<h1><a class="anchor" id="autotoc_md78"></a>
	FlatBuffers Go library code location</h1>
	<p>The code for the FlatBuffers Go library can be found at <code>flatbuffers/go</code>. You can browse the library code on the <a href="https://github.com/google/flatbuffers/tree/master/go">FlatBuffers GitHub page</a>.</p>
	<h1><a class="anchor" id="autotoc_md79"></a>
	Testing the FlatBuffers Go library</h1>
	<p>The code to test the Go library can be found at <code>flatbuffers/tests</code>. The test code itself is located in <a href="https://github.com/google/
	flatbuffers/blob/master/tests/go_test.go">go_test.go</a>.</p>
	<p>To run the tests, use the <a href="https://github.com/google/flatbuffers/
	blob/master/tests/GoTest.sh">GoTest.sh</a> shell script.</p>
	<p><em>Note: The shell script requires <a href="https://golang.org/doc/install">Go</a> to be installed.</em></p>
	<h1><a class="anchor" id="autotoc_md80"></a>
	Using the FlatBuffers Go library</h1>
	<p><em>Note: See <a class="el" href="flatbuffers_guide_tutorial.html">Tutorial</a> for a more in-depth example of how to use FlatBuffers in Go.</em></p>
	<p>FlatBuffers supports reading and writing binary FlatBuffers in Go.</p>
	<p>To use FlatBuffers in your own code, first generate Go classes from your schema with the <code>--go</code> option to <code>flatc</code>. Then you can include both FlatBuffers and the generated code to read or write a FlatBuffer.</p>
	<p>For example, here is how you would read a FlatBuffer binary file in Go: First, include the library and generated code. Then read a FlatBuffer binary file into a <code>[]byte</code>, which you pass to the <code>GetRootAsMonster</code> function:</p>
	<div class="fragment"><div class="line">import (</div>
	<div class="line"> example "MyGame/Example"</div>
	<div class="line"> flatbuffers "github.com/google/flatbuffers/go"</div>
	<div class="line"> </div>
	<div class="line"> io/ioutil</div>
	<div class="line">)</div>
	<div class="line"> </div>
	<div class="line">buf, err := ioutil.ReadFile("monster.dat")</div>
	<div class="line">// handle err</div>
	<div class="line">monster := example.GetRootAsMonster(buf, 0)</div>
	</div><!-- fragment --><p>Now you can access values like this:</p>
	<div class="fragment"><div class="line">hp := monster.Hp()</div>
	<div class="line">pos := monster.Pos(nil)</div>
	</div><!-- fragment --><p>In some cases it's necessary to modify values in an existing FlatBuffer in place (without creating a copy). For this reason, scalar fields of a Flatbuffer table or struct can be mutated.</p>
	<div class="fragment"><div class="line">monster := example.GetRootAsMonster(buf, 0)</div>
	<div class="line"> </div>
	<div class="line">// Set table field.</div>
	<div class="line">if ok := monster.MutateHp(10); !ok {</div>
	<div class="line"> panic("failed to mutate Hp")</div>
	<div class="line">}</div>
	<div class="line"> </div>
	<div class="line">// Set struct field.</div>
	<div class="line">monster.Pos().MutateZ(4)</div>
	<div class="line"> </div>
	<div class="line">// This mutation will fail because the mana field is not available in</div>
	<div class="line">// the buffer. It should be set when creating the buffer.</div>
	<div class="line">if ok := monster.MutateMana(20); !ok {</div>
	<div class="line"> panic("failed to mutate Hp")</div>
	<div class="line">}</div>
	</div><!-- fragment --><p>The term <code>mutate</code> is used instead of <code>set</code> to indicate that this is a special use case. All mutate functions return a boolean value which is false if the field we're trying to mutate is not available in the buffer.</p>
	<h1><a class="anchor" id="autotoc_md81"></a>
	Text Parsing</h1>
	<p>There currently is no support for parsing text (Schema's and JSON) directly from Go, though you could use the C++ parser through cgo. Please see the C++ documentation for more on text parsing.</p>
	<p><br />
	</p>
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