alextanhongpin / mapper

golang code generation to map one struct to another struct

mapper

Generate code that maps struct to struct.

Similar projects:

• builder: generate builder for private fields
• getter: generate getters for private struct fields, with inlining

Design thoughts

• should not include pointer. Mapping requires one struct and returns one struct or error.
• should not allow context (?). Is there a need to pass context in mapping?
• Elem refers to the base type, so slice or pointer type User has Elem User

See the examples folder for results.

Basic

Field

The mapper should be able to map type A to type B, given that both types:

• both must have the same number of fields the target fields can be more than the source fields, and they may reference the same source fields. All target fields must have a corresponding mapping from the source fields, unless they are ignored.
• both must not be a pointer (it does not make sense for mapping pointer to non-pointer) sql.NullString can be converted to pointer string. As long as there are imported functions that allows the transformation, it should be valid
• both names must match, and could be altered through alias
• both types must match. If there is an imported function F, then the param P must match the source S and the result R must match the target T. F(P)->R is F(S)->T

type Mapper interface {
	AtoB (A) B
}

type A struct {
	ID string
}

type B struct {
	ID string
}

Expected:

type MapperImpl struct {}

func (m MapperImpl) AtoB(a A) B {
	return B{
		ID: a.ID
	}
}

Method

When A has a method that maps to the name of B's field, we should be able to use that.

• if that method returns a tuple error, AtoB should also return a tuple error
• both names must match
• both types must match

type Mapper interface {
	AtoB (A) B
}

type A struct {
	id string
}
func (a A) ID() string {
	return a.id
}

type B struct {
	ID string
}

Expected:

type MapperImpl struct {}

func (m MapperImpl) AtoB(a A) B {
	return B{
		ID: a.ID()
	}
}

Error

Nested

Slice and Variadic

Tags

Renaming Field and Methods

Ignore

Func

Interface and Struct

TODO

• better error handling
• handle exported and private fields
• refactor using TDD