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Deepcopier

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This package is meant to make copying of structs to/from others structs a bit easier.

Installation

go get -u github.com/ulule/deepcopier

Usage

// Deep copy instance1 into instance2
Copy(instance1).To(instance2)

// Deep copy instance1 into instance2 and passes the following context (which
// is basically a map[string]interface{}) as first argument
// to methods of instance2 that defined the struct tag "context".
Copy(instance1).WithContext(map[string]interface{}{"foo": "bar"}).To(instance2)

// Deep copy instance2 into instance1
Copy(instance1).From(instance2)

// Deep copy instance2 into instance1 and passes the following context (which
// is basically a map[string]interface{}) as first argument
// to methods of instance1 that defined the struct tag "context".
Copy(instance1).WithContext(map[string]interface{}{"foo": "bar"}).From(instance2)

Available options for deepcopier struct tag:

OptionDescription
fieldField or method name in source instance
skipIgnores the field
contextTakes a map[string]interface{} as first argument (for methods)
forceSet the value of a sql.Null* field (instead of copying the struct)

Options example:

type Source struct {
    Name                         string
    SkipMe                       string
    SQLNullStringToSQLNullString sql.NullString
    SQLNullStringToString        sql.NullString

}

func (Source) MethodThatTakesContext(c map[string]interface{}) string {
    return "whatever"
}

type Destination struct {
    FieldWithAnotherNameInSource      string         `deepcopier:"field:Name"`
    SkipMe                            string         `deepcopier:"skip"`
    MethodThatTakesContext            string         `deepcopier:"context"`
    SQLNullStringToSQLNullString      sql.NullString 
    SQLNullStringToString             string         `deepcopier:"force"`
}

Example:

package main

import (
    "fmt"
 
    "github.com/ulule/deepcopier"
)

// Model
type User struct {
    // Basic string field
    Name  string
    // Deepcopier supports https://golang.org/pkg/database/sql/driver/#Valuer
    Email sql.NullString
}

func (u *User) MethodThatTakesContext(ctx map[string]interface{}) string {
    // do whatever you want
    return "hello from this method"
}

// Resource
type UserResource struct {
    DisplayName            string `deepcopier:"field:Name"`
    SkipMe                 string `deepcopier:"skip"`
    MethodThatTakesContext string `deepcopier:"context"`
    Email                  string `deepcopier:"force"`

}

func main() {
    user := &User{
        Name: "gilles",
        Email: sql.NullString{
            Valid: true,
            String: "gilles@example.com",
        },
    }

    resource := &UserResource{}

    deepcopier.Copy(user).To(resource)

    fmt.Println(resource.DisplayName)
    fmt.Println(resource.Email)
}

Looking for more information about the usage?

We wrote an introduction article. Have a look and feel free to give us your feedback.

Contributing

Don't hesitate ;)