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gorm


			
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        <li class="chapter " data-level="1.1" data-path="./">
            
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                        <b>1.1.</b>
                    
                    Getting Started with GORM
            
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                        <b>1.2.</b>
                    
                    Database
            
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                        <b>1.2.1.</b>
                    
                    Database Connection
            
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                        <b>1.2.2.</b>
                    
                    Migration
            
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                        <b>1.3.</b>
                    
                    Models
            
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                        <b>1.3.1.</b>
                    
                    Model Definition
            
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                        <b>1.3.2.</b>
                    
                    Conventions & Overriding
            
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                        <b>1.3.3.</b>
                    
                    Associations
            
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                        <b>1.3.3.1.</b>
                    
                    Belongs To
            
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                        <b>1.3.3.2.</b>
                    
                    Has One
            
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                        <b>1.3.3.3.</b>
                    
                    Has Many
            
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                        <b>1.3.3.4.</b>
                    
                    Many To Many
            
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                        <b>1.3.3.5.</b>
                    
                    Polymorphism
            
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                        <b>1.3.3.6.</b>
                    
                    Association Mode
            
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                        <b>1.3.4.</b>
                    
                    Dialect Specific Data Type
            
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                        <b>1.4.</b>
                    
                    CRUD: Reading and Writing Data
            
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                        <b>1.4.1.</b>
                    
                    Create
            
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                        <b>1.4.2.</b>
                    
                    Query
            
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                        <b>1.4.3.</b>
                    
                    Preloading (Eager Loading)
            
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                        <b>1.4.4.</b>
                    
                    Update
            
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                        <b>1.4.5.</b>
                    
                    Delete / Soft Delete
            
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                        <b>1.4.6.</b>
                    
                    Associations
            
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                        <b>1.5.</b>
                    
                    Callbacks
            
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                        <b>1.6.</b>
                    
                    Advanced Usage
            
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                        <b>1.6.1.</b>
                    
                    Error Handling
            
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                        <b>1.6.2.</b>
                    
                    Transactions
            
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                        <b>1.6.3.</b>
                    
                    Raw SQL & SQL Builder
            
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                        <b>1.6.4.</b>
                    
                    Generic database interface sql.DB
            
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                        <b>1.6.5.</b>
                    
                    Composite Primary Key
            
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                        <b>1.6.6.</b>
                    
                    Overriding Logger
            
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                        <b>1.7.</b>
                    
                    Development
            
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                        <b>1.7.1.</b>
                    
                    Architecture
            
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                        <b>1.7.2.</b>
                    
                    Write Plugins
            
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                        <b>1.8.</b>
                    
                    Change Log
            
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                                <section class="normal markdown-section">
                                
                                <h1 id="development">Development</h1>
<!-- toc -->
<h2 id="architecture">Architecture</h2>
<p>Gorm use chainable API, <code>*gorm.DB</code> is the bridge of chains, for each chain API, it will create a new relation.</p>
<pre><code class="lang-go">db, err := gorm.Open(<span class="hljs-string">&quot;postgres&quot;</span>, <span class="hljs-string">&quot;user=gorm dbname=gorm sslmode=disable&quot;</span>)

<span class="hljs-comment">// create a new relation</span>
db = db.Where(<span class="hljs-string">&quot;name = ?&quot;</span>, <span class="hljs-string">&quot;jinzhu&quot;</span>)

<span class="hljs-comment">// filter even more</span>
<span class="hljs-keyword">if</span> SomeCondition {
    db = db.Where(<span class="hljs-string">&quot;age = ?&quot;</span>, <span class="hljs-number">20</span>)
} <span class="hljs-keyword">else</span> {
    db = db.Where(<span class="hljs-string">&quot;age = ?&quot;</span>, <span class="hljs-number">30</span>)
}
<span class="hljs-keyword">if</span> YetAnotherCondition {
    db = db.Where(<span class="hljs-string">&quot;active = ?&quot;</span>, <span class="hljs-number">1</span>)
}
</code></pre>
<p>When we start to perform any operations, GORM will create a new <code>*gorm.Scope</code> instance based on current <code>*gorm.DB</code></p>
<pre><code class="lang-go"><span class="hljs-comment">// perform a querying operation</span>
db.First(&amp;user)
</code></pre>
<p>And based on current operation&apos;s type, it will call registered <code>creating</code>, <code>updating</code>, <code>querying</code>, <code>deleting</code> or <code>row_querying</code> callbacks to run the operation.</p>
<p>For above example, will call <code>querying</code> callbacks, refer <a href="callbacks.html#querying-an-object">Querying Callbacks</a></p>
<h2 id="write-plugins">Write Plugins</h2>
<p>GORM itself is powered by <code>Callbacks</code>, so you could fully customize GORM as you want</p>
<h3 id="register-a-new-callback">Register a new callback</h3>
<pre><code class="lang-go"><span class="hljs-keyword">func</span> updateCreated(scope *Scope) {
    <span class="hljs-keyword">if</span> scope.HasColumn(<span class="hljs-string">&quot;Created&quot;</span>) {
        scope.SetColumn(<span class="hljs-string">&quot;Created&quot;</span>, NowFunc())
    }
}

db.Callback().Create().Register(<span class="hljs-string">&quot;update_created_at&quot;</span>, updateCreated)
<span class="hljs-comment">// register a callback for Create process</span>
</code></pre>
<h3 id="delete-an-existing-callback">Delete an existing callback</h3>
<pre><code class="lang-go">db.Callback().Create().Remove(<span class="hljs-string">&quot;gorm:create&quot;</span>)
<span class="hljs-comment">// delete callback `gorm:create` from Create callbacks</span>
</code></pre>
<h3 id="replace-an-existing-callback">Replace an existing callback</h3>
<pre><code class="lang-go">db.Callback().Create().Replace(<span class="hljs-string">&quot;gorm:create&quot;</span>, newCreateFunction)
<span class="hljs-comment">// replace callback `gorm:create` with new function `newCreateFunction` for Create process</span>
</code></pre>
<h3 id="register-callback-orders">Register callback orders</h3>
<pre><code class="lang-go">db.Callback().Create().Before(<span class="hljs-string">&quot;gorm:create&quot;</span>).Register(<span class="hljs-string">&quot;update_created_at&quot;</span>, updateCreated)
db.Callback().Create().After(<span class="hljs-string">&quot;gorm:create&quot;</span>).Register(<span class="hljs-string">&quot;update_created_at&quot;</span>, updateCreated)
db.Callback().Query().After(<span class="hljs-string">&quot;gorm:query&quot;</span>).Register(<span class="hljs-string">&quot;my_plugin:after_query&quot;</span>, afterQuery)
db.Callback().Delete().After(<span class="hljs-string">&quot;gorm:delete&quot;</span>).Register(<span class="hljs-string">&quot;my_plugin:after_delete&quot;</span>, afterDelete)
db.Callback().Update().Before(<span class="hljs-string">&quot;gorm:update&quot;</span>).Register(<span class="hljs-string">&quot;my_plugin:before_update&quot;</span>, beforeUpdate)
db.Callback().Create().Before(<span class="hljs-string">&quot;gorm:create&quot;</span>).After(<span class="hljs-string">&quot;gorm:before_create&quot;</span>).Register(<span class="hljs-string">&quot;my_plugin:before_create&quot;</span>, beforeCreate)
</code></pre>
<h3 id="pre-defined-callbacks">Pre-Defined Callbacks</h3>
<p>GORM has defiend callbacks to perform its CRUD operations, check them out before start write your plugins</p>
<ul>
<li><p><a href="https://github.com/jinzhu/gorm/blob/master/callback_create.go" target="_blank">Create callbacks</a></p>
</li>
<li><p><a href="https://github.com/jinzhu/gorm/blob/master/callback_update.go" target="_blank">Update callbacks</a></p>
</li>
<li><p><a href="https://github.com/jinzhu/gorm/blob/master/callback_query.go" target="_blank">Query callbacks</a></p>
</li>
<li><p><a href="https://github.com/jinzhu/gorm/blob/master/callback_delete.go" target="_blank">Delete callbacks</a></p>
</li>
<li><p>Row Query callbacks</p>
</li>
</ul>
<p>Row Query callbacks will be called when run <code>Row</code> or <code>Rows</code>, by default there is no registered callbacks for it, you could register a new one like:</p>
<pre><code class="lang-go"><span class="hljs-keyword">func</span> updateTableName(scope *gorm.Scope) {
  scope.Search.Table(scope.TableName() + <span class="hljs-string">&quot;_draft&quot;</span>) <span class="hljs-comment">// append `_draft` to table name</span>
}

db.Callback().RowQuery().Register(<span class="hljs-string">&quot;publish:update_table_name&quot;</span>, updateTableName)
</code></pre>
<p>View <a href="https://godoc.org/github.com/jinzhu/gorm" target="_blank">https://godoc.org/github.com/jinzhu/gorm</a> to view all available API</p>

                                
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