gorm/models.html
2016-02-26 21:58:36 +08:00

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Getting Started with GORM
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<b>1.</b>
Database
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Database Connection
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<b>1.2.</b>
Migration
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<b>2.</b>
Models
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<b>2.1.</b>
Model Defination
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<b>2.2.</b>
Naming Conventions &amp; Overriding
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<b>2.3.</b>
Associations
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<b>2.3.1.</b>
Belongs To
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<b>2.3.2.</b>
Has One
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<b>2.3.3.</b>
Has Many
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<b>2.3.4.</b>
Many To Many
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<b>2.3.5.</b>
Polymorphism
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<b>2.3.6.</b>
Association Mode
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<b>3.</b>
CRUD: Reading and Writing Data
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<b>3.1.</b>
Create
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<b>3.2.</b>
Query
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<b>3.3.</b>
Preloading (Eager Loading)
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<b>3.4.</b>
Update
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<b>3.5.</b>
Delete / Soft Delete
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<b>4.</b>
Callbacks
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Advanced Usage
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<b>5.1.</b>
Error Handling
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<b>5.2.</b>
Transactions
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<b>5.3.</b>
Raw SQL &amp; SQL Builder
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<b>5.4.</b>
Composite Primary Key
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<b>5.5.</b>
Overriding Logger
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<b>6.</b>
Development
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Write Plugins
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<h1 id="models">Models</h1>
<!-- toc -->
<ul>
<li><a href="#model-defination">Model Defination</a></li>
<li><a href="#conventions-overriding-conventions">Conventions &amp; Overriding Conventions</a><ul>
<li><a href="#gormmodel-struct"><code>gorm.Model</code> struct</a></li>
<li><a href="#table-name-is-the-pluralized-version-of-struct-name">Table name is the pluralized version of struct name</a></li>
<li><a href="#column-name-is-the-snake-case-of-fields-name">Column name is the snake case of field&apos;s name</a></li>
<li><a href="#field-id-as-primary-key">Field <code>ID</code> as primary key</a></li>
<li><a href="#field-createdat-used-to-store-records-created-time">Field <code>CreatedAt</code> used to store record&apos;s created time</a></li>
<li><a href="#use-updatedat-used-to-store-records-updated-time">Use <code>UpdatedAt</code> used to store record&apos;s updated time</a></li>
<li><a href="#use-deletedat-to-store-records-deleted-time-if-field-exists">Use <code>DeletedAt</code> to store record&apos;s deleted time if field exists</a></li>
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<!-- toc stop -->
<h2 id="model-defination">Model Defination</h2>
<pre><code class="lang-go"><span class="token keyword">type</span> User <span class="token keyword">struct</span> <span class="token operator">{</span>
gorm<span class="token operator">.</span>Model
Birthday time<span class="token operator">.</span>Time
Age <span class="token builtin">int</span>
Name <span class="token builtin">string</span> <span class="token string">`sql:&quot;size:255&quot;`</span> <span class="token comment" spellcheck="true">// Default size for string is 255, you could reset it with this tag</span>
Num <span class="token builtin">int</span> <span class="token string">`sql:&quot;AUTO_INCREMENT&quot;`</span>
IgnoreMe <span class="token builtin">int</span> <span class="token string">`sql:&quot;-&quot;`</span> <span class="token comment" spellcheck="true">// Ignore this field</span>
<span class="token operator">}</span>
</code></pre>
<h2 id="conventions--overriding-conventions">Conventions &amp; Overriding Conventions</h2>
<h3 id="gormmodel-struct"><code>gorm.Model</code> struct</h3>
<p>Gorm has defined struct <code>gorm.Model</code>, which could be embeded in your models, it will add fields <code>ID</code>, <code>CreatedAt</code>, <code>UpdatedAt</code>, <code>DeletedAt</code> to your model</p>
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Model&apos;s definition</span>
<span class="token keyword">type</span> Model <span class="token keyword">struct</span> <span class="token operator">{</span>
ID <span class="token builtin">uint</span> <span class="token string">`gorm:&quot;primary_key&quot;`</span>
CreatedAt time<span class="token operator">.</span>Time
UpdatedAt time<span class="token operator">.</span>Time
DeletedAt <span class="token operator">*</span>time<span class="token operator">.</span>Time
<span class="token operator">}</span>
</code></pre>
<h3 id="table-name-is-the-pluralized-version-of-struct-name">Table name is the pluralized version of struct name</h3>
<pre><code class="lang-go"><span class="token keyword">type</span> User <span class="token keyword">struct</span> <span class="token operator">{</span><span class="token operator">}</span> <span class="token comment" spellcheck="true">// default table name is `users`</span>
<span class="token comment" spellcheck="true">// set User&apos;s table name to be `profiles</span>
<span class="token keyword">type</span> <span class="token operator">(</span>User<span class="token operator">)</span> <span class="token function">TableName<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token builtin">string</span> <span class="token operator">{</span>
<span class="token keyword">return</span> <span class="token string">&quot;profiles&quot;</span>
<span class="token operator">}</span>
<span class="token keyword">func</span> <span class="token operator">(</span>u User<span class="token operator">)</span> <span class="token function">TableName<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token builtin">string</span> <span class="token operator">{</span>
<span class="token keyword">if</span> u<span class="token operator">.</span>Role <span class="token operator">==</span> <span class="token string">&quot;admin&quot;</span> <span class="token operator">{</span>
<span class="token keyword">return</span> <span class="token string">&quot;admin_users&quot;</span>
<span class="token operator">}</span> <span class="token keyword">else</span> <span class="token operator">{</span>
<span class="token keyword">return</span> <span class="token string">&quot;users&quot;</span>
<span class="token operator">}</span>
<span class="token operator">}</span>
<span class="token comment" spellcheck="true">// Disable table name&apos;s pluralization globally</span>
db<span class="token operator">.</span><span class="token function">SingularTable<span class="token punctuation">(</span></span><span class="token boolean">true</span><span class="token operator">)</span> <span class="token comment" spellcheck="true">// if set this to true, `User`&apos;s default table name will be `user`, table name setted with `TableName` won&apos;t be affected</span>
</code></pre>
<h3 id="column-name-is-the-snake-case-of-fields-name">Column name is the snake case of field&apos;s name</h3>
<pre><code class="lang-go"><span class="token keyword">type</span> User <span class="token keyword">struct</span> <span class="token operator">{</span>
ID <span class="token builtin">uint</span> <span class="token comment" spellcheck="true">// column name will be `id`</span>
Name <span class="token builtin">string</span> <span class="token comment" spellcheck="true">// column name will be `name`</span>
Birthday time<span class="token operator">.</span>Time <span class="token comment" spellcheck="true">// column name will be `birthday`</span>
CreatedAt time<span class="token operator">.</span>Time <span class="token comment" spellcheck="true">// column name will be `created_at`</span>
<span class="token operator">}</span>
<span class="token keyword">type</span> Animal <span class="token keyword">struct</span> <span class="token operator">{</span>
AnimalId <span class="token builtin">int64</span> <span class="token string">`gorm:&quot;column:beast_id&quot;`</span> <span class="token comment" spellcheck="true">// set column name to `beast_id`</span>
Birthday time<span class="token operator">.</span>Time <span class="token string">`gorm:&quot;column:day_of_the_beast&quot;`</span> <span class="token comment" spellcheck="true">// set column name to `day_of_the_beast`</span>
Age <span class="token builtin">int64</span> <span class="token string">`gorm:&quot;column:age_of_the_beast&quot;`</span> <span class="token comment" spellcheck="true">// set column name to `age_of_the_beast`</span>
<span class="token operator">}</span>
</code></pre>
<h3 id="field-id-as-primary-key">Field <code>ID</code> as primary key</h3>
<pre><code class="lang-go"><span class="token keyword">type</span> User <span class="token keyword">struct</span> <span class="token operator">{</span>
ID <span class="token builtin">uint</span> <span class="token comment" spellcheck="true">// field named `ID` is the default primary key for `User`</span>
Name <span class="token builtin">string</span>
<span class="token operator">}</span>
<span class="token comment" spellcheck="true">// your could also use tag `primary_key` to set other field as primary key</span>
<span class="token keyword">type</span> Animal <span class="token keyword">struct</span> <span class="token operator">{</span>
AnimalId <span class="token builtin">int64</span> <span class="token string">`gorm:&quot;primary_key&quot;`</span> <span class="token comment" spellcheck="true">// set AnimalId to be primary key</span>
Name <span class="token builtin">string</span>
Age <span class="token builtin">int64</span>
<span class="token operator">}</span>
</code></pre>
<h3 id="field-createdat-used-to-store-records-created-time">Field <code>CreatedAt</code> used to store record&apos;s created time</h3>
<p>Create records having <code>CreatedAt</code> field will set it to current time.</p>
<pre><code class="lang-go">db<span class="token operator">.</span><span class="token function">Create<span class="token punctuation">(</span></span><span class="token operator">&amp;</span>user<span class="token operator">)</span> <span class="token comment" spellcheck="true">// will set `CreatedAt` to current time</span>
<span class="token comment" spellcheck="true">// To change its value, you could use `Update`</span>
db<span class="token operator">.</span><span class="token function">Model<span class="token punctuation">(</span></span><span class="token operator">&amp;</span>user<span class="token operator">)</span><span class="token operator">.</span><span class="token function">Update<span class="token punctuation">(</span></span><span class="token string">&quot;CreatedAt&quot;</span><span class="token operator">,</span> time<span class="token operator">.</span><span class="token function">Now<span class="token punctuation">(</span></span><span class="token operator">)</span><span class="token operator">)</span>
</code></pre>
<h3 id="use-updatedat-used-to-store-records-updated-time">Use <code>UpdatedAt</code> used to store record&apos;s updated time</h3>
<p>Save records having <code>UpdatedAt</code> field will set it to current time.</p>
<pre><code class="lang-go">db<span class="token operator">.</span><span class="token function">Save<span class="token punctuation">(</span></span><span class="token operator">&amp;</span>user<span class="token operator">)</span> <span class="token comment" spellcheck="true">// will set `UpdatedAt` to current time</span>
db<span class="token operator">.</span><span class="token function">Model<span class="token punctuation">(</span></span><span class="token operator">&amp;</span>user<span class="token operator">)</span><span class="token operator">.</span><span class="token function">Update<span class="token punctuation">(</span></span><span class="token string">&quot;name&quot;</span><span class="token operator">,</span> <span class="token string">&quot;jinzhu&quot;</span><span class="token operator">)</span> <span class="token comment" spellcheck="true">// will set `UpdatedAt` to current time</span>
</code></pre>
<h3 id="use-deletedat-to-store-records-deleted-time-if-field-exists">Use <code>DeletedAt</code> to store record&apos;s deleted time if field exists</h3>
<p>Delete records having <code>DeletedAt</code> field, it won&apos;t delete the record from database, but will set field <code>DeletedAt</code>&apos;s value to current time.</p>
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