Like encoding/json but stores graphs instead of trees.

Grison solves the following problems:

• Loops in the graph.
• Encoding and decoding of interface types.

Given that there's no obvious "starting point" in a graph and, in fact, there may not be a single node from which all the other nodes are reachable, grison requires that you create a "master" structure, i.e. a structure with pointers to all the nodes:

type Master struct{
    Foo []*Foo
    Bar []*Bar
}

You can then marshal/unmarshal this master structure as needed:

var m1 Master
...
b, err := grison.Marshal(&m1)
...
var m2 Master
err = grison.Unmarshal(b, &m2)

Struct tags work very much the same as with encoding/json:

type Person struct {
   Age int `grison:"age,omitempty"`
}

To get indented output, use Prefix and Indent options.

b, err := MarshalWithOpts(m, MarshalOpts{
    Prefix: "> ",
    Indent: "  ",
})

Node IDs in the JSON file are automatically generated (#1, #2 etc.) However, if GetIDs option is set, GetID function will be called on each node and the result will be used as the ID. If a node doesn't implement GetID function, marshaling will fail with an appropriate error.

b, err := MarshalWithOpts(m, MarshalOpts{
    GetIDs: true,
})

At the moment there are no unmarshal options.

type Parent struct {
    Name     string
    Sex      string
    Spouse   *Parent
    Children []*Child
}

type Child struct {
    Name   string
    Age    int
    Father *Parent
    Mother *Parent
}

type Master struct {
    Parents  []*Parent
    Children []*Child
}

The data structures above can produce, for example, the following JSON:

{
    "Children": {
        "#3": {
            "Age": 10,
            "Father": {"$ref": "Parents:#2"},
            "Mother": {"$ref": "Parents:#1"},
            "Name": "Carol"
        },
        "#4": {
            "Age": 8,
            "Father": {"$ref": "Parents:#2"},
            "Mother": {"$ref": "Parents:#1"},
            "Name": "Dan"
        }
    },
    "Parents": {
        "#1": {
            "Children": [
                {"$ref": "Children:#3"},
                {"$ref": "Children:#4"}
            ],
            "Name": "Alice",
            "Sex": "Female",
            "Spouse": {"$ref": "Parents:#2"}
        },
        "#2": {
            "Children": [
                {"$ref": "Children:#3"},
                {"$ref": "Children:#4"}
            ],
            "Name": "Bob",
            "Sex": "Male",
            "Spouse": {"$ref": "Parents:#1"}
        }
    }
}