contractor (for golang)

Contractor allows you to dynamically populate structs. This package was made because I have multiple versions of the same struct. You could compare it to the versions used in API's. ( You end up with multiple versions over years, and sometimes need to support more than one version, migration time for clients...)

Based on the selected version (In the URL or the Header, whatever you like) we retrieve an map of structs. We now can select the actual struct we need, set some values and finally send it back to the screen OR send it over to the DB (In my case gorp).

Still working on a proper description :)

Getting started

First of all install the package with go get "go get github.com/donseba/contractor" Add it to your imports where you want to use it.

Structured Struct Layout

Basically we are going to store an reference to the struct in an map[string]map[string]interface{} ..say wut?

And it would look like something like this :

var TestContracts = map[string]map[string]interface{}{
	"01": map[string]interface{}{
		"Struct1": v1.Struct1{},
		"Struct2": v1.Struct2{},
	},
	"02": map[string]interface{}{
		"Struct1": v2.Struct1{},
		"Struct2": v2.Struct2{},
	},
}

As you can see, the first level contains the version of the struct.

The second level is the most tricky parts.

keys You always have to make sure all versions contain the same keys. Well it is not mandatory, but since it is so dynamic we have to set some ground rules.

values The values contain the struct reference.

Usage

// Get the set of contracts which hold a map of structs assigned to version 01
contractSet := contractor.NewContractor(models.TestContracts["01"])

// Read the struct and assign it to an value in case we want to send.
Struct1, err := contractSet.Read("Struct1")
if err != nil {
  // Do your typical error handling here
}

// Create some dummy data like Json.Unmarshal()  
dummyData := make(map[string]interface{})
dummyData["Field1"] = "valField1"
dummyData["Field2"] = "valField2"

// Assign the dummy data to the Struct.
Struct1.Set(dummyData)

The above example clearly only works if we have an valid v01.struct1{} Having 2 fields Field1 & Field2

package v01

type Struct1 struct {
	Field1        string
	Field2        string
}

Output

To get the whole case you can use the following :

//Read from the Struct
fmt.Printf( "%+v\n", Struct1.Get() )

resulting in :

&{Field1:valField1 Field2:valField2}

Or you could get the JSON :

fmt.Fprintf(w, "%s", Struct1.Json())

resulting in :

{"Field1":"valField1","Field2":"valField2"}

To get an specific item of an case, you can do the following :

Struct1.Item("Field1")

The naming convention of "Item()" might change to "Line()"

Working with nested structs. ( Since 0.2.0 )

lets say your structs has a nested struct.

package v01

type Struct1 struct {
	Field1        string
	Field2        string
	InnerStruct   struct{
		SubField1 string
		SubField2 struct{
			SubSubField1 string
		}
	}
}

It is Possible to assign values to the InnerStruct fields by doing the following :

Struct1, err := contractSet.Read("Struct1")
if err != nil {
  // Do your typical error handling here
}

// Create some dummy data like
dummyData := make(map[string]interface{})
dummyData["Field1"] = "valField1"
dummyData["Field2"] = "valField2"
dummyData["InnerStruct.SubField1"] = "SubFieldVal1"
dummyData["InnerStruct.SubField2.SubSubField1"] = "SubSubFieldVal1"

// Assign the dummy data to the Struct.
Struct1.Set(dummyData)

License

This package is open-sourced software licensed under the MIT license

donseba / contractor