urlstruct decodes url.Values into structs

Example

Following example decodes URL query ?page=2&limit=100&author_id=123 into a struct and uses go-pg feature WhereStruct to autogenerate WHERE clause:

type Book struct {
    tableName struct{} `pg:"alias:b"`

    ID        int64
    AuthorID  int64
    CreatedAt time.Time
}

type BookFilter struct {
    tableName struct{} `urlstruct:"b"`

    urlstruct.Pager
    AuthorID int64
}

func ExampleUnmarshal_filter() {
    db := pg.Connect(&pg.Options{
        User:     "postgres",
        Password: "",
        Database: "postgres",
    })
    defer db.Close()

    values := url.Values{
        "author_id": {"123"},
        "page":      {"2"},
        "limit":     {"100"},
    }
    filter := new(BookFilter)
    err := urlstruct.Unmarshal(values, filter)
    if err != nil {
        panic(err)
    }

    filter.Pager.MaxLimit = 100     // default max limit is 1000
    filter.Pager.MaxOffset = 100000 // default max offset is 1000000

    // Following query generates:
    //
    // SELECT "b"."id", "b"."author_id", "b"."created_at"
    // FROM "books" AS "b"
    // WHERE "b".author_id = 123
    // LIMIT 100 OFFSET 100

    var books []*Book
    _ = db.Model(&books).
        WhereStruct(filter).
        Limit(filter.Pager.GetLimit()).
        Offset(filter.Pager.GetOffset()).
        Select()

    fmt.Println("author", filter.AuthorID)
    fmt.Println("limit", filter.GetLimit())
    fmt.Println("offset", filter.GetLimit())
    // Output: author 123
    // limit 100
    // offset 100
}