Golang structure for nested objects

php editor Apple shared a detailed introduction to the structure used for nested objects in the Golang language. In Golang, the nested object structure is a powerful feature that allows us to nest other structures or interface types within a structure. Through the structure of nested objects, we can easily combine and reuse code, improving the readability and maintainability of the code. Not only that, the structure of nested objects can also achieve the effect of multiple inheritance, allowing us to design and build complex data structures more flexibly. In this article, we will discuss in detail the methods and techniques of using the structure of nested objects in Golang to help readers better understand and apply this feature.

Question content

I am currently using gofiber v2 to create golang api.

I have the following document structure for a music track in a mongo database:

{
    "_id" : objectid("63cc26cb86ae1611380e1206"),
    "active" : 1,
    "exclusive" : "false",
    "track_title" : "burn slow (sting)",
    "artist_id" : "395",
    "artist_name" : "david hollandsworth",
    "album_title" : "cult justice 23",
    "composer" : "david hollandsworth",
    "duration" : "00:16",
    "publisher" : "fliktrax, llc",
    "description" : "t.v. drama, rural tension, apprehension. style: \"hell on wheels\" soundtrack.",
    "url_path" : "davidhollandsworth/cultjustice23/burn-slow-sting.wav",
    "vocal_type" : "instrumental",
    "beats_per_minute" : "80",
    "file_path_compressed" : "davidhollandsworth/cultjustice23/burn-slow-sting.mp3",
    "file_path_uncompressed" : "davidhollandsworth/cultjustice23/burn-slow-sting.wav",

    "genres" : [ 
        "tension", 
        "americana", 
        "tv drama"
    ],
    "genres_keys" : [ 
        "tension", 
        "americana", 
        "tv drama"
    ],
    "moods" : [ 
        "tension", 
        "bluesy", 
        "spacey"
    ],
    "styles" : [ 
        "tv drama", 
        "unsolved mystery", 
        "western"
    ],
    "instruments" : [ 
        "dobro", 
        "banjo", 
        "percussion"
    ],
    "keywords" : [ 
        "rural-tension", 
        " showdown", 
        " apprehension", 
        " uncertainty", 
        " light-tension", 
        " strings-tension", 
        " heartland", 
        " trouble", 
        " uneasy", 
        " cautious", 
        " outlaw", 
        " yellowstone", 
        " bayou", 
        " gritty", 
        " swampy", 
        " swamp-people", 
        " southern", 
        " uncertain", 
        " drama", 
        " apprehension", 
        " bluesy", 
        " blues", 
        " shack", 
        " poor-folk", 
        " primitive"
    ],
    "sounds_like" : [ 
        "brian tyler", 
        "max richter", 
        "t.v. drama"
    ],
    "resembles_song" : [ 
        "hell on wheels", 
        "yellowstone", 
        "rural/outlaw/tension"
    ],
    "last_modified" : 1674323659,
    "variation_count" : 5,
    "variations" : {
        "_id" : objectid("63cc26bc86ae1611380e1200"),
        "track_title" : "burn slow",
        "artist_name" : "david hollandsworth",
        "master_track_id" : "63cc26bc86ae1611380e1200",
        "master_track" : objectid("63cc26bc86ae1611380e1200"),
        "merged" : 1,
        "variation_count" : 5,
        "variations" : {
            "63cc26bc86ae1611380e1200" : {
                "track_id" : "63cc26bc86ae1611380e1200",
                "track_title" : "burn slow",
                "artist_name" : "david hollandsworth"
            },
            "63cc26c086ae1611380e1203" : {
                "track_id" : "63cc26c086ae1611380e1203",
                "track_title" : "burn slow (bed mix)",
                "artist_name" : "david hollandsworth"
            },
            "63cc26c386ae1611380e1204" : {
                "track_id" : "63cc26c386ae1611380e1204",
                "track_title" : "burn slow (cutdown)",
                "artist_name" : "david hollandsworth"
            },
            "63cc26c786ae1611380e1205" : {
                "track_id" : "63cc26c786ae1611380e1205",
                "track_title" : "burn slow (lows and perc)",
                "artist_name" : "david hollandsworth"
            },
            "63cc26cb86ae1611380e1206" : {
                "track_id" : "63cc26cb86ae1611380e1206",
                "track_title" : "burn slow (sting)",
                "artist_name" : "david hollandsworth"
            }
        }
    }
}

Currently, I have the following track structure in my golang model:

type Track struct {
    ID                   primitive.ObjectID `bson:"_id, omitempty" json:"_id"`
    TrackTitle           string             `bson:"track_title" json:"track_title"`
    ArtistId             string             `bson:"artist_id" json:"artist_id"`
    ArtistName           string             `bson:"artist_name" json:"artist_name"`
    AlbumTitle           string             `bson:"album_title" json:"album_title"`
    Composer             string             `bson:"composer" json:"composer"`
    Publisher            string             `bson:"publisher" json:"publisher"`
    Description          string             `bson:"description" json:"description"`
    Duration             string             `bson:"duration" json:"duration"`
    UrlPath              string             `bson:"url_path" json:"url_path"`
    VocalType            string             `bson:"vocal_type" json:"vocal_type"`
    BeatsPerMinute       string             `bson:"beats_per_minute" json:"beats_per_minute"`
    FilePathCompressed   string             `bson:"file_path_compressed" json:"bfile_path_compressed"`
    FilePathUncompressed string             `bson:"file_path_uncompressed" json:"file_path_uncompressed"`
    PreviewURL           string             `bson:"preview_url" json:"preview_url"`
    Genres               []interface{}      `bson:"genres" json:"genres"`
    GenresKeys           []interface{}      `bson:"genres_keys" json:"genres_keys"`
    Moods                []interface{}      `bson:"moods" json:"moods"`
    Styles               []interface{}      `bson:"styles" json:"styles"`
    Instruments          []interface{}      `bson:"instruments" json:"instruments"`
    Keywords             []interface{}      `bson:"keywords" json:"keywords"`
    SoundsLike           []interface{}      `bson:"sounds_like" json:"sounds_like"`
    ResemblesSong        []interface{}      `bson:"resembles_song" json:"resembles_song"`
    LastModified         int                `bson:"last_modified" json:"last_modified"`
    VariationCount       int                `bson:"variation_count" json:"variation_count"`
}

Currently all document fields are correctly decoded to json, but I'm now stuck on how to construct the embedded "variations.variations" field (note that there are variations within variations). The structure of the embedded variant is an object without a key, but a dynamic mongo id string.

I tried implementing custom struct and interface types but without success.

If anyone has encountered this problem before, any help would be greatly appreciated.

Solution

I recommend avoiding interface{} (or any) if possible and use concrete types. For example. genres is an array of strings, using []string in go.

For variations.variations fields, you can use map as well as string keys and struct types describing their elements.

type Track struct {
    ID                   primitive.ObjectID `bson:"_id, omitempty" json:"_id"`
    TrackTitle           string             `bson:"track_title" json:"track_title"`
    ArtistId             string             `bson:"artist_id" json:"artist_id"`
    ArtistName           string             `bson:"artist_name" json:"artist_name"`
    AlbumTitle           string             `bson:"album_title" json:"album_title"`
    Composer             string             `bson:"composer" json:"composer"`
    Publisher            string             `bson:"publisher" json:"publisher"`
    Description          string             `bson:"description" json:"description"`
    Duration             string             `bson:"duration" json:"duration"`
    UrlPath              string             `bson:"url_path" json:"url_path"`
    VocalType            string             `bson:"vocal_type" json:"vocal_type"`
    BeatsPerMinute       string             `bson:"beats_per_minute" json:"beats_per_minute"`
    FilePathCompressed   string             `bson:"file_path_compressed" json:"bfile_path_compressed"`
    FilePathUncompressed string             `bson:"file_path_uncompressed" json:"file_path_uncompressed"`
    PreviewURL           string             `bson:"preview_url" json:"preview_url"`
    Genres               []string           `bson:"genres" json:"genres"`
    GenresKeys           []string           `bson:"genres_keys" json:"genres_keys"`
    Moods                []string           `bson:"moods" json:"moods"`
    Styles               []string           `bson:"styles" json:"styles"`
    Instruments          []string           `bson:"instruments" json:"instruments"`
    Keywords             []string           `bson:"keywords" json:"keywords"`
    SoundsLike           []string           `bson:"sounds_like" json:"sounds_like"`
    ResemblesSong        []string           `bson:"resembles_song" json:"resembles_song"`
    LastModified         int                `bson:"last_modified" json:"last_modified"`
    VariationCount       int                `bson:"variation_count" json:"variation_count"`
    Variations           Variations         `bson:"variations" json:"variations"`
}

type Variations struct {
    ID             primitive.ObjectID   `bson:"_id" json:"_id"`
    TrackTitle     string               `bson:"track_title" json:"track_title"`
    ArtistName     string               `bson:"artist_name" json:"artist_name"`
    MasterTrackID  string               `bson:"master_track_id" json:"master_track_id"`
    MasterTrack    primitive.ObjectID   `bson:"master_track" json:"master_track"`
    Merged         int                  `bson:"merged" json:"merged"`
    VariationCount int                  `bson:"variation_count" json:"variation_count"`
    Variations     map[string]Variation `bson:"variations" json:"variations"`
}

type Variation struct {
    TrackID    string `bson:"track_id" json:"track_id"`
    TrackTitle string `bson:"track_title" json:"track_title"`
    ArtistName string `bson:"artist_name" json:"artist_name"`
}

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