Support for map of struct

[zenthangplus]

I've modified these codes to support for map

• Map of struct
• Map of ptr struct

Related #28

[creasty]

Thank you for the PR.
I'm swamped this week, so it might take some time to review.

[creasty]

Some test cases are failing.
(CI didn't run on the fork PRs due to insufficient configuration so I run locally.)

$ go test ./...
--- FAIL: TestInit (0.00s)
    --- FAIL: TestInit/map_of_ptr_struct (0.00s)
        defaults_test.go:602: it should set default for Bar field in Struct1 item
        defaults_test.go:605: it should set default for WithDefault field in Struct1 item
        defaults_test.go:608: it should not override Foo field in Struct2 item
        defaults_test.go:614: it should set default for WithDefault field in Struct2 item
FAIL
FAIL    github.com/creasty/defaults     0.095s
?       github.com/creasty/defaults/internal/fixture    [no test files]
FAIL

[zenthangplus]

@creasty fixed, i've mistake when write new value to map.

[creasty]

Sorry for the delayed response.

[creasty]

Delving in on my side, this feels more elegant and can support even more complex types like map[string]map[int]Struct, map[string]*map[int]Struct,map[string]AliasOfSliceOfStruct, etc.

		for _, e := range field.MapKeys() {
			var v = field.MapIndex(e)

			switch v.Kind() {
			case reflect.Ptr:
				switch v.Elem().Kind() {
				case reflect.Struct, reflect.Slice, reflect.Map:
					if err := setField(v.Elem(), ""); err != nil {
						return err
					}
				}
			case reflect.Struct, reflect.Slice, reflect.Map:
				ref := reflect.New(v.Type())
				ref.Elem().Set(v)
				if err := setField(ref.Elem(), ""); err != nil {
					return err
				}
				field.SetMapIndex(e, ref.Elem().Convert(v.Type()))
			}
		}