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go run -mod=mod entgo.io/ent/cmd/ent init User

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// User在User实体中组合了ent默认的数据库模式定义
type User struct {
    ent.Schema
}

// User的字段
func (User) Fields() []ent.Field {
    return nil
}

// User的边
func (User) Edges() []ent.Edge {
    return nil
}

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// User的字段
func (User) Fields() []ent.Field {
    return []ent.Field{
        field.Int("age").
            Positive(),
        field.String("name").
            Default("unknown"),
    }
}

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go generate ./ent

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package main

import (
	"context"
	"log"

	"<project>/ent"

	_ "github.com/lib/pq"
)

func main() {
	client, err := ent.Open("postgres", "host=<host> port=<port> user=<user> dbname=<database> password=<pass>")
	if err != nil {
		log.Fatalf("failed opening connection to postgres: %v", err)
	}
	defer client.Close()
	// 运行自动迁移工具。
	if err := client.Schema.Create(context.Background()); err != nil {
		log.Fatalf("failed creating schema resources: %v", err)
	}
}

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package main

import (
    "context"
    "log"

    "<project>/ent"

    _ "github.com/mattn/go-sqlite3"
)

func main() {
    client, err := ent.Open("sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
    if err != nil {
        log.Fatalf("failed opening connection to sqlite: %v", err)
    }
    defer client.Close()
    // 运行自动迁移工具。
    if err := client.Schema.Create(context.Background()); err != nil {
        log.Fatalf("failed creating schema resources: %v", err)
    }
}

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package main

import (
    "context"
    "log"

    "<project>/ent"

    _ "github.com/go-sql-driver/mysql"
)

func main() {
    client, err := ent.Open("mysql", "<user>:<pass>@tcp(<host>:<port>)/<database>?parseTime=True")
    if err != nil {
        log.Fatalf("failed opening connection to mysql: %v", err)
    }
    defer client.Close()
    // 运行自动迁移工具。
    if err := client.Schema.Create(context.Background()); err != nil {
        log.Fatalf("failed creating schema resources: %v", err)
    }
}

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func CreateUser(ctx context.Context, client *ent.Client) (*ent.User, error) {
    u, err := client.User.
        Create().
        SetAge(30).
        SetName("a8m").
        Save(ctx)
    if err != nil {
        return nil, fmt.Errorf("failed creating user: %w", err)
    }
    log.Println("user was created: ", u)
    return u, nil
}

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func QueryUser(ctx context.Context, client *ent.Client) (*ent.User, error) {
    u, err := client.User.
        Query().
        Where(user.Name("a8m")).
        // `Only` 如果没有发现用户则报错,
        // 否则正常返回。
        Only(ctx)
    if err != nil {
        return nil, fmt.Errorf("failed querying user: %w", err)
    }
    log.Println("user returned: ", u)
    return u, nil
}