forked from mirror/gorm
71 lines
2.7 KiB
Markdown
71 lines
2.7 KiB
Markdown
# Gorm Development
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<!-- toc -->
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## Architecture
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The most notable component of Gorm is`gorm.DB`, which hold database connection. It could be initialized like this:
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db, err := gorm.Open("postgres", "user=gorm dbname=gorm sslmode=disable")
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Gorm has chainable API, `gorm.DB` is the bridge of chains, it save related information and pass it to the next chain.
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Lets use below code to explain how it works:
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db.Where("name = ?", "jinzhu").Find(&users)
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// equivalent code
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newdb := db.Where("name =?", "jinzhu")
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newdb.Find(&user)
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`newdb` is `db`'s clone, in addition, it contains search conditions from the `Where` method.
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`Find` is a query method, it creates a `Scope` instance, and pass it as argument to query callbacks.
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There are four kinds of callbacks corresponds to sql's CURD: create callbacks, update callbacks, query callbacks, delete callbacks.
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## Callbacks
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### Register a new callback
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func updateCreated(scope *Scope) {
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if scope.HasColumn("Created") {
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scope.SetColumn("Created", NowFunc())
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}
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}
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db.Callback().Create().Register("update_created_at", updateCreated)
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// register a callback for Create process
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### Delete an existing callback
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db.Callback().Create().Remove("gorm:create")
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// delete callback `gorm:create` from Create callbacks
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### Replace an existing callback
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db.Callback().Create().Replace("gorm:create", newCreateFunction)
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// replace callback `gorm:create` with new function `newCreateFunction` for Create process
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### Register callback orders
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db.Callback().Create().Before("gorm:create").Register("update_created_at", updateCreated)
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db.Callback().Create().After("gorm:create").Register("update_created_at", updateCreated)
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db.Callback().Query().After("gorm:query").Register("my_plugin:after_query", afterQuery)
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db.Callback().Delete().After("gorm:delete").Register("my_plugin:after_delete", afterDelete)
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db.Callback().Update().Before("gorm:update").Register("my_plugin:before_update", beforeUpdate)
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db.Callback().Create().Before("gorm:create").After("gorm:before_create").Register("my_plugin:before_create", beforeCreate)
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### Callback API
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Gorm is powered by callbacks, so you could refer below links to learn how to write callbacks
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[Create callbacks](https://github.com/jinzhu/gorm/blob/master/callback_create.go)
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[Update callbacks](https://github.com/jinzhu/gorm/blob/master/callback_update.go)
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[Query callbacks](https://github.com/jinzhu/gorm/blob/master/callback_query.go)
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[Delete callbacks](https://github.com/jinzhu/gorm/blob/master/callback_delete.go)
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View [https://github.com/jinzhu/gorm/blob/master/scope.go](https://github.com/jinzhu/gorm/blob/master/scope.go) for all available API
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