64 lines
1.4 KiB
Go
64 lines
1.4 KiB
Go
// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import (
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"encoding/json"
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"fmt"
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"log"
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)
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// database is responsible for encoding and decoding a list.
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type database struct {
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list *list
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}
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func (db *database) UnmarshalJSON(data []byte) error {
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// Provides a concrete data structure that we can use to decode.
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// It is a slice of structs.
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var decodables []struct {
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Type string // The product type.
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Item json.RawMessage // The raw item data (from database.json)
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}
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// First, decode the "Type" part.
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// Leave the "Item" as raw json data.
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if err := json.Unmarshal(data, &decodables); err != nil {
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log.Fatalln(err)
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}
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// Decode the "Item" part for each json object.
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for _, d := range decodables {
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it, err := db.newItem(d.Item, d.Type)
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if err != nil {
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return err
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}
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*db.list = append(*db.list, it)
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}
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return nil
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}
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// newItem decodes and returns a product type wrapped in an item iface value.
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func (*database) newItem(data []byte, itemType string) (it item, _ error) {
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switch itemType {
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default:
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return nil, fmt.Errorf("newItem: type (%q) does not exist", itemType)
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case "book":
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it = new(book)
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case "puzzle":
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it = new(puzzle)
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case "game":
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it = new(game)
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case "toy":
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it = new(toy)
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}
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return it, json.Unmarshal(data, &it)
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}
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