Prototype in Go
Prototype is a creational design pattern that allows cloning objects, even complex ones, without coupling to their specific classes.
All prototype classes should have a common interface that makes it possible to copy objects even if their concrete classes are unknown. Prototype objects can produce full copies since objects of the same class can access each other’s private fields.
Conceptual Example
Let’s try to figure out the Prototype pattern using an example based on the operating system’s file system. The OS file system is recursive: the folders contain files and folders, which may also include files and folders, and so on.
Each file and folder can be represented by an inode interface. inode interface also has the clone function.
Both file and folder structs implement the print and clone functions since they are of the inode type. Also, notice the clone function in both file and folder. The clone function in both of them returns a copy of the respective file or folder. During the cloning, we append the suffix “_clone” to the name field.
inode.go: Prototype interface
package main type Inode interface { print(string) clone() Inode } file.go: Concrete prototype
package main import "fmt" type File struct { name string } func (f *File) print(indentation string) { fmt.Println(indentation + f.name) } func (f *File) clone() Inode { return &File{name: f.name + "_clone"} } folder.go: Concrete prototype
package main import "fmt" type Folder struct { children []Inode name string } func (f *Folder) print(indentation string) { fmt.Println(indentation + f.name) for _, i := range f.children { i.print(indentation + indentation) } } func (f *Folder) clone() Inode { cloneFolder := &Folder{name: f.name + "_clone"} var tempChildren []Inode for _, i := range f.children { copy := i.clone() tempChildren = append(tempChildren, copy) } cloneFolder.children = tempChildren return cloneFolder } main.go: Client code
package main import "fmt" func main() { file1 := &File{name: "File1"} file2 := &File{name: "File2"} file3 := &File{name: "File3"} folder1 := &Folder{ children: []Inode{file1}, name: "Folder1", } folder2 := &Folder{ children: []Inode{folder1, file2, file3}, name: "Folder2", } fmt.Println("\nPrinting hierarchy for Folder2") folder2.print(" ") cloneFolder := folder2.clone() fmt.Println("\nPrinting hierarchy for clone Folder") cloneFolder.print(" ") } output.txt: Execution result
Printing hierarchy for Folder2 Folder2 Folder1 File1 File2 File3 Printing hierarchy for clone Folder Folder2_clone Folder1_clone File1_clone File2_clone File3_clone 
