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<html xmlns:cf="http://docbook.sourceforge.net/xmlns/chunkfast/1.0"><head><meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"><title>Relations and Tuples</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.0"><link rel="start" href="index.html" title="GLib Reference Manual"><link rel="up" href="glib-data-types.html" title="GLib Data Types"><link rel="prev" href="glib-Datasets.html" title="Datasets"><link rel="next" href="glib-Caches.html" title="Caches"><meta name="generator" content="GTK-Doc V1.4 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"><link rel="chapter" href="glib.html" title="GLib Overview"><link rel="chapter" href="glib-fundamentals.html" title="GLib Fundamentals"><link rel="chapter" href="glib-core.html" title="GLib Core Application Support"><link rel="chapter" href="glib-utilities.html" title="GLib Utilities"><link rel="chapter" href="glib-data-types.html" title="GLib Data Types"><link rel="chapter" href="tools.html" title="GLib Tools"><link rel="index" href="ix01.html" title="Index"><link rel="index" href="ix02.html" title="Index of deprecated symbols"><link rel="index" href="ix03.html" title="Index of new symbols in 2.2"><link rel="index" href="ix04.html" title="Index of new symbols in 2.4"><link rel="index" href="ix05.html" title="Index of new symbols in 2.6"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><table class="navigation" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle"><td><a accesskey="p" href="glib-Datasets.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td><td><a accesskey="u" href="glib-data-types.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td><td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td><th width="100%" align="center">GLib Reference Manual</th><td><a accesskey="n" href="glib-Caches.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td></tr></table><div class="refentry" lang="en"><a name="glib-Relations-and-Tuples"></a><div class="titlepage"></div><div class="refnamediv"><table width="100%"><tr><td valign="top"><h2><span class="refentrytitle">Relations and Tuples</span></h2><p>Relations and Tuples — tables of data which can be indexed on any number of fields.</p></td><td valign="top" align="right"></td></tr></table></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">#include <glib.h> <a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a>;<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a>* <a href="glib-Relations-and-Tuples.html#g-relation-new">g_relation_new</a> (<a href="glib-Basic-Types.html#gint">gint</a> fields);void <a href="glib-Relations-and-Tuples.html#g-relation-index">g_relation_index</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, <a href="glib-Basic-Types.html#gint">gint</a> field, <a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_func, <a href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);void <a href="glib-Relations-and-Tuples.html#g-relation-insert">g_relation_insert</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, ...);<a href="glib-Basic-Types.html#gboolean">gboolean</a> <a href="glib-Relations-and-Tuples.html#g-relation-exists">g_relation_exists</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, ...);<a href="glib-Basic-Types.html#gint">gint</a> <a href="glib-Relations-and-Tuples.html#g-relation-count">g_relation_count</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, <a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key, <a href="glib-Basic-Types.html#gint">gint</a> field);<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a>* <a href="glib-Relations-and-Tuples.html#g-relation-select">g_relation_select</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, <a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key, <a href="glib-Basic-Types.html#gint">gint</a> field);<a href="glib-Basic-Types.html#gint">gint</a> <a href="glib-Relations-and-Tuples.html#g-relation-delete">g_relation_delete</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, <a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key, <a href="glib-Basic-Types.html#gint">gint</a> field);void <a href="glib-Relations-and-Tuples.html#g-relation-destroy">g_relation_destroy</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation);void <a href="glib-Relations-and-Tuples.html#g-relation-print">g_relation_print</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation); <a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a>;void <a href="glib-Relations-and-Tuples.html#g-tuples-destroy">g_tuples_destroy</a> (<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a> *tuples);<a href="glib-Basic-Types.html#gpointer">gpointer</a> <a href="glib-Relations-and-Tuples.html#g-tuples-index">g_tuples_index</a> (<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a> *tuples, <a href="glib-Basic-Types.html#gint">gint</a> index_, <a href="glib-Basic-Types.html#gint">gint</a> field);</pre></div><div class="refsect1" lang="en"><a name="id3199190"></a><h2>Description</h2><p>A <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> is a table of data which can be indexed on any number of fields,rather like simple database tables. A <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> contains a number ofrecords, called tuples. Each record contains a number of fields.Records are not ordered, so it is not possible to find the record at aparticular index.</p><p>Note that <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> tables are currently limited to 2 fields.</p><p>To create a GRelation, use <a href="glib-Relations-and-Tuples.html#g-relation-new"><code class="function">g_relation_new()</code></a>.</p><p>To specify which fields should be indexed, use <a href="glib-Relations-and-Tuples.html#g-relation-index"><code class="function">g_relation_index()</code></a>.Note that this must be called before any tuples are added to the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</p><p>To add records to a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> use <a href="glib-Relations-and-Tuples.html#g-relation-insert"><code class="function">g_relation_insert()</code></a>.</p><p>To determine if a given record appears in a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, use<a href="glib-Relations-and-Tuples.html#g-relation-exists"><code class="function">g_relation_exists()</code></a>. Note that fields are compared directly, so pointersmust point to the exact same position (i.e. different copies of the samestring will not match.)</p><p>To count the number of records which have a particular value in a givenfield, use <a href="glib-Relations-and-Tuples.html#g-relation-count"><code class="function">g_relation_count()</code></a>.</p><p>To get all the records which have a particular value in a given field,use <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a>. To access fields of the resulting records,use <a href="glib-Relations-and-Tuples.html#g-tuples-index"><code class="function">g_tuples_index()</code></a>. To free the resulting records use <a href="glib-Relations-and-Tuples.html#g-tuples-destroy"><code class="function">g_tuples_destroy()</code></a>.</p><p>To delete all records which have a particular value in a given field,use <a href="glib-Relations-and-Tuples.html#g-relation-delete"><code class="function">g_relation_delete()</code></a>.</p><p>To destroy the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, use <a href="glib-Relations-and-Tuples.html#g-relation-destroy"><code class="function">g_relation_destroy()</code></a>.</p><p>To help debug <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> objects, use <a href="glib-Relations-and-Tuples.html#g-relation-print"><code class="function">g_relation_print()</code></a>.</p></div><div class="refsect1" lang="en"><a name="id3199429"></a><h2>Details</h2><div class="refsect2" lang="en"><a name="id3199435"></a><h3><a name="GRelation"></a>GRelation</h3><a class="indexterm" name="id3199445"></a><pre class="programlisting">typedef struct _GRelation GRelation;</pre><p>The <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> struct is an opaque data structure to represent a<a href="glib-Relations-and-Tuples.html" title="Relations and Tuples">Relation</a>.It should only be accessed via the following functions.</p></div><hr><div class="refsect2" lang="en"><a name="id3199479"></a><h3><a name="g-relation-new"></a>g_relation_new ()</h3><a class="indexterm" name="id3199488"></a><pre class="programlisting"><a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a>* g_relation_new (<a href="glib-Basic-Types.html#gint">gint</a> fields);</pre><p>Creates a new <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> with the given number of fields.Note that currently the number of fields must be 2.</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><em class="parameter"><code>fields</code></em> :</span></td><td>the number of fields.</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>a new <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id3199563"></a><h3><a name="g-relation-index"></a>g_relation_index ()</h3><a class="indexterm" name="id3199573"></a><pre class="programlisting">void g_relation_index (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, <a href="glib-Basic-Types.html#gint">gint</a> field, <a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_func, <a href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);</pre><p>Creates an index on the given field.Note that this must be called before any records are added to the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><em class="parameter"><code>relation</code></em> :</span></td><td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</td></tr><tr><td><span class="term"><em class="parameter"><code>field</code></em> :</span></td><td>the field to index, counting from 0.</td></tr><tr><td><span class="term"><em class="parameter"><code>hash_func</code></em> :</span></td><td>a function to produce a hash value from the field data.</td></tr><tr><td><span class="term"><em class="parameter"><code>key_equal_func</code></em> :</span></td><td>a function to compare two values of the given field.</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id3199703"></a><h3><a name="g-relation-insert"></a>g_relation_insert ()</h3><a class="indexterm" name="id3199714"></a><pre class="programlisting">void g_relation_insert (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, ...);</pre><p>Inserts a record into a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><em class="parameter"><code>relation</code></em> :</span></td><td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</td></tr><tr><td><span class="term"><em class="parameter"><code>...</code></em> :</span></td><td>the fields of the record to add. This must match the number offields in the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id3199799"></a><h3><a name="g-relation-exists"></a>g_relation_exists ()</h3><a class="indexterm" name="id3199810"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gboolean">gboolean</a> g_relation_exists (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation, ...);</pre><p>Returns <code class="literal">TRUE</code> if a record with the given values exists in a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.Note that the values are compared directly, so that, for example, twocopies of the same string will not match.</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><em class="parameter"><code>relation</code></em> :</span></td><td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</td></tr><tr><td><span class="term"><em class="parameter"><code>...</code></em> :</span></td><td>the fields of the record to compare. The number must match thenumber of fields in the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td><code class="literal">TRUE</code> if a record matches.</td></tr></tbody>⌨️ 快捷键说明
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