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# Copier
I am a copier, I copy everything from one to another
[](https://github.com/jinzhu/copier/actions)
## Features
* Copy from field to field with same name
* Copy from method to field with same name
* Copy from field to method with same name
* Copy from slice to slice
* Copy from struct to slice
* Copy from map to map
* Enforce copying a field with a tag
* Ignore a field with a tag
* Deep Copy
## Usage
```go
package main
import (
"fmt"
"github.com/jinzhu/copier"
)
type User struct {
Name string
Role string
Age int32
EmployeCode int64 `copier:"EmployeNum"` // specify field name
// Explicitly ignored in the destination struct.
Salary int
}
func (user *User) DoubleAge() int32 {
return 2 * user.Age
}
// Tags in the destination Struct provide instructions to copier.Copy to ignore
// or enforce copying and to panic or return an error if a field was not copied.
type Employee struct {
// Tell copier.Copy to panic if this field is not copied.
Name string `copier:"must"`
// Tell copier.Copy to return an error if this field is not copied.
Age int32 `copier:"must,nopanic"`
// Tell copier.Copy to explicitly ignore copying this field.
Salary int `copier:"-"`
DoubleAge int32
EmployeId int64 `copier:"EmployeNum"` // specify field name
SuperRole string
}
func (employee *Employee) Role(role string) {
employee.SuperRole = "Super " + role
}
func main() {
var (
user = User{Name: "Jinzhu", Age: 18, Role: "Admin", Salary: 200000}
users = []User{{Name: "Jinzhu", Age: 18, Role: "Admin", Salary: 100000}, {Name: "jinzhu 2", Age: 30, Role: "Dev", Salary: 60000}}
employee = Employee{Salary: 150000}
employees = []Employee{}
)
copier.Copy(&employee, &user)
fmt.Printf("%#v \n", employee)
// Employee{
// Name: "Jinzhu", // Copy from field
// Age: 18, // Copy from field
// Salary:150000, // Copying explicitly ignored
// DoubleAge: 36, // Copy from method
// EmployeeId: 0, // Ignored
// SuperRole: "Super Admin", // Copy to method
// }
// Copy struct to slice
copier.Copy(&employees, &user)
fmt.Printf("%#v \n", employees)
// []Employee{
// {Name: "Jinzhu", Age: 18, Salary:0, DoubleAge: 36, EmployeId: 0, SuperRole: "Super Admin"}
// }
// Copy slice to slice
employees = []Employee{}
copier.Copy(&employees, &users)
fmt.Printf("%#v \n", employees)
// []Employee{
// {Name: "Jinzhu", Age: 18, Salary:0, DoubleAge: 36, EmployeId: 0, SuperRole: "Super Admin"},
// {Name: "jinzhu 2", Age: 30, Salary:0, DoubleAge: 60, EmployeId: 0, SuperRole: "Super Dev"},
// }
// Copy map to map
map1 := map[int]int{3: 6, 4: 8}
map2 := map[int32]int8{}
copier.Copy(&map2, map1)
fmt.Printf("%#v \n", map2)
// map[int32]int8{3:6, 4:8}
}
```
### Copy with Option
```go
copier.CopyWithOption(&to, &from, copier.Option{IgnoreEmpty: true, DeepCopy: true})
```
## Contributing
You can help to make the project better, check out [http://gorm.io/contribute.html](http://gorm.io/contribute.html) for things you can do.
# Author
**jinzhu**
* <http://github.com/jinzhu>
* <wosmvp@gmail.com>
* <http://twitter.com/zhangjinzhu>
## License
Released under the [MIT License](https://github.com/jinzhu/copier/blob/master/License).
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