80 lines
2.6 KiB
Markdown
80 lines
2.6 KiB
Markdown
- [GORM](#gorm)
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- [QuickStart](#quickstart)
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- [Declaring Models](#declaring-models)
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# GORM
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## QuickStart
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GORM为golang的orm框架，其使用示例如下：
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```go
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package main
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import (
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"gorm.io/gorm"
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"gorm.io/driver/sqlite"
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)
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type Product struct {
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gorm.Model
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Code string
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Price uint
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}
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func main() {
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db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})
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if err != nil {
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panic("failed to connect database")
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}
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// Migrate the schema
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db.AutoMigrate(&Product{})
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// Create
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db.Create(&Product{Code: "D42", Price: 100})
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// Read
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var product Product
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db.First(&product, 1) // find product with integer primary key
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db.First(&product, "code = ?", "D42") // find product with code D42
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// Update - update product's price to 200
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db.Model(&product).Update("Price", 200)
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// Update - update multiple fields
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db.Model(&product).Updates(Product{Price: 200, Code: "F42"}) // non-zero fields
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db.Model(&product).Updates(map[string]interface{}{"Price": 200, "Code": "F42"})
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// Delete - delete product
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db.Delete(&product, 1)
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}
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```
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## Declaring Models
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gorm中，Model通过struct来进行定义，struct中的fields可以为如下类型：
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- 基础golang类型
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- 指针
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- type alias
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- 自定义类型
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- 自定义类型需要实现`database/sql`中的Scanner和Valuer接口
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如下为一个Model定义的示例：
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```go
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type User struct {
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ID uint // Standard field for the primary key
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Name string // A regular string field
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Email *string // A pointer to a string, allowing for null values
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Age uint8 // An unsigned 8-bit integer
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Birthday *time.Time // A pointer to time.Time, can be null
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MemberNumber sql.NullString // Uses sql.NullString to handle nullable strings
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ActivatedAt sql.NullTime // Uses sql.NullTime for nullable time fields
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CreatedAt time.Time // Automatically managed by GORM for creation time
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UpdatedAt time.Time // Automatically managed by GORM for update time
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ignored string // fields that aren't exported are ignored
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}
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```
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在上述Model中
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- 基础类型的字段可以直接访问，例如`uint, uint8, string`等
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- 指针类型，例如`*time.Time, *string`等，代表该字段值可为空
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- `sql/database`中的`sql.NullString`和`sql.NullTime`类型，也代表该字段可为空
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- `CreateAt`字段和`UpdatedAt`字段是由Gorm管理的字段，当Record被创建或更新时，该字段的值会自动被注入为当前时间
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- `Non-exported fields`（首字母不是大写）并不会被映射
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