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Associations
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Belongs To
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Has One
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Has Many
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Polymorphism
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<b>1.3.3.6.</b>
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<b>1.4.1.</b>
Create
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Query
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<b>1.4.4.</b>
Update
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Delete / Soft Delete
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Associations
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Callbacks
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Advanced Usage
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Error Handling
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<b>1.6.2.</b>
Transactions
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Raw SQL & SQL Builder
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Composite Primary Key
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Overriding Logger
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Development
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Architecture
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<h1 id="models">Models</h1>
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<h2 id="model-definition">Model Definition</h2>
<pre><code class="lang-go"><span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
gorm.Model
Birthday time.Time
Age <span class="hljs-keyword">int</span>
Name <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:&quot;size:255&quot;`</span> <span class="hljs-comment">// Default size for string is 255, reset it with this tag</span>
Num <span class="hljs-keyword">int</span> <span class="hljs-string">`gorm:&quot;AUTO_INCREMENT&quot;`</span>
CreditCard CreditCard <span class="hljs-comment">// One-To-One relationship (has one - use CreditCard&apos;s UserID as foreign key)</span>
Emails []Email <span class="hljs-comment">// One-To-Many relationship (has many - use Email&apos;s UserID as foreign key)</span>
BillingAddress Address <span class="hljs-comment">// One-To-One relationship (belongs to - use BillingAddressID as foreign key)</span>
BillingAddressID sql.NullInt64
ShippingAddress Address <span class="hljs-comment">// One-To-One relationship (belongs to - use ShippingAddressID as foreign key)</span>
ShippingAddressID <span class="hljs-keyword">int</span>
IgnoreMe <span class="hljs-keyword">int</span> <span class="hljs-string">`gorm:&quot;-&quot;`</span> <span class="hljs-comment">// Ignore this field</span>
Languages []Language <span class="hljs-string">`gorm:&quot;many2many:user_languages;&quot;`</span> <span class="hljs-comment">// Many-To-Many relationship, &apos;user_languages&apos; is join table</span>
}
<span class="hljs-keyword">type</span> Email <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">int</span>
UserID <span class="hljs-keyword">int</span> <span class="hljs-string">`gorm:&quot;index&quot;`</span> <span class="hljs-comment">// Foreign key (belongs to), tag `index` will create index for this column</span>
Email <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:&quot;type:varchar(100);unique_index&quot;`</span> <span class="hljs-comment">// `type` set sql type, `unique_index` will create unique index for this column</span>
Subscribed <span class="hljs-keyword">bool</span>
}
<span class="hljs-keyword">type</span> Address <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">int</span>
Address1 <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:&quot;not null;unique&quot;`</span> <span class="hljs-comment">// Set field as not nullable and unique</span>
Address2 <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:&quot;type:varchar(100);unique&quot;`</span>
Post sql.NullString <span class="hljs-string">`gorm:&quot;not null&quot;`</span>
}
<span class="hljs-keyword">type</span> Language <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">int</span>
Name <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:&quot;index:idx_name_code&quot;`</span> <span class="hljs-comment">// Create index with name, and will create combined index if find other fields defined same name</span>
Code <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:&quot;index:idx_name_code&quot;`</span> <span class="hljs-comment">// `unique_index` also works</span>
}
<span class="hljs-keyword">type</span> CreditCard <span class="hljs-keyword">struct</span> {
gorm.Model
UserID <span class="hljs-keyword">uint</span>
Number <span class="hljs-keyword">string</span>
}
</code></pre>
<h2 id="conventions">Conventions</h2>
<h3 id="gormmodel-struct"><code>gorm.Model</code> struct</h3>
<p>Base model definition <code>gorm.Model</code>, including fields <code>ID</code>, <code>CreatedAt</code>, <code>UpdatedAt</code>, <code>DeletedAt</code>, you could embed it in your model, or only write those fields you want</p>
<pre><code class="lang-go"><span class="hljs-comment">// Base Model&apos;s definition</span>
<span class="hljs-keyword">type</span> Model <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">uint</span> <span class="hljs-string">`gorm:&quot;primary_key&quot;`</span>
CreatedAt time.Time
UpdatedAt time.Time
DeletedAt *time.Time
}
<span class="hljs-comment">// Add fields `ID`, `CreatedAt`, `UpdatedAt`, `DeletedAt`</span>
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
gorm.Model
Name <span class="hljs-keyword">string</span>
}
<span class="hljs-comment">// Only need field `ID`, `CreatedAt`</span>
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">uint</span>
CreatedAt time.Time
Name <span class="hljs-keyword">string</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="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {} <span class="hljs-comment">// default table name is `users`</span>
<span class="hljs-comment">// set User&apos;s table name to be `profiles`</span>
<span class="hljs-keyword">func</span> (User) TableName() <span class="hljs-keyword">string</span> {
<span class="hljs-keyword">return</span> <span class="hljs-string">&quot;profiles&quot;</span>
}
<span class="hljs-keyword">func</span> (u User) TableName() <span class="hljs-keyword">string</span> {
<span class="hljs-keyword">if</span> u.Role == <span class="hljs-string">&quot;admin&quot;</span> {
<span class="hljs-keyword">return</span> <span class="hljs-string">&quot;admin_users&quot;</span>
} <span class="hljs-keyword">else</span> {
<span class="hljs-keyword">return</span> <span class="hljs-string">&quot;users&quot;</span>
}
}
<span class="hljs-comment">// Disable table name&apos;s pluralization globally</span>
db.SingularTable(<span class="hljs-literal">true</span>) <span class="hljs-comment">// 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="change-default-tablenames">Change default tablenames</h3>
<p>You can apply any rules on the default table name by defining the <code>DefaultTableNameHandler</code></p>
<pre><code class="lang-go">gorm.DefaultTableNameHandler = <span class="hljs-keyword">func</span> (db *gorm.DB, defaultTableName <span class="hljs-keyword">string</span>) <span class="hljs-keyword">string</span> {
<span class="hljs-keyword">return</span> <span class="hljs-string">&quot;prefix_&quot;</span> + defaultTableName;
}
</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="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">uint</span> <span class="hljs-comment">// column name will be `id`</span>
Name <span class="hljs-keyword">string</span> <span class="hljs-comment">// column name will be `name`</span>
Birthday time.Time <span class="hljs-comment">// column name will be `birthday`</span>
CreatedAt time.Time <span class="hljs-comment">// column name will be `created_at`</span>
}
<span class="hljs-comment">// Overriding Column Name</span>
<span class="hljs-keyword">type</span> Animal <span class="hljs-keyword">struct</span> {
AnimalId <span class="hljs-keyword">int64</span> <span class="hljs-string">`gorm:&quot;column:beast_id&quot;`</span> <span class="hljs-comment">// set column name to `beast_id`</span>
Birthday time.Time <span class="hljs-string">`gorm:&quot;column:day_of_the_beast&quot;`</span> <span class="hljs-comment">// set column name to `day_of_the_beast`</span>
Age <span class="hljs-keyword">int64</span> <span class="hljs-string">`gorm:&quot;column:age_of_the_beast&quot;`</span> <span class="hljs-comment">// set column name to `age_of_the_beast`</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="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
ID <span class="hljs-keyword">uint</span> <span class="hljs-comment">// field named `ID` will be the default primary field</span>
Name <span class="hljs-keyword">string</span>
}
<span class="hljs-comment">// Set a field to be primary field with tag `primary_key`</span>
<span class="hljs-keyword">type</span> Animal <span class="hljs-keyword">struct</span> {
AnimalId <span class="hljs-keyword">int64</span> <span class="hljs-string">`gorm:&quot;primary_key&quot;`</span> <span class="hljs-comment">// set AnimalId to be primary key</span>
Name <span class="hljs-keyword">string</span>
Age <span class="hljs-keyword">int64</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.Create(&amp;user) <span class="hljs-comment">// will set `CreatedAt` to current time</span>
<span class="hljs-comment">// To change its value, you could use `Update`</span>
db.Model(&amp;user).Update(<span class="hljs-string">&quot;CreatedAt&quot;</span>, time.Now())
</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"><span class="hljs-comment">// Whenever one or more `user` fields are edited using Save() or Update(), `UpdatedAt` will be set to current time</span>
db.Save(&amp;user) <span class="hljs-comment">// will set `UpdatedAt` to current time</span>
db.Model(&amp;user).Update(<span class="hljs-string">&quot;name&quot;</span>, <span class="hljs-string">&quot;jinzhu&quot;</span>) <span class="hljs-comment">// 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 be deleted from database, but only set field <code>DeletedAt</code>&apos;s value to current time, and the record is not findable when querying, refer <a href="crud.html#soft-delete">Soft Delete</a></p>
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