golang nested struct and map

Question

I am new to golang and trying to map database query result to my struct which is nested but I am getting errors and not able to figure out the best way to do it. This program is suppose to out JSON - book details group by categories.

Struct is as follows

type book struct{
  category string
  books []*bookDetails
}

type bookDetails struct{
  name  string
  id    uint
  publisher string.
}

Expected JSON output

[
  {
    "category" : "Ficton",
    "books" : [
               {name:'aaa',id:12,publisher:'one'},
               {name:'bbb',id:13,publisher:'two'}
             ]
  },
 {
    "category" : "suspense",
    "books" : [
               {name:'ccc',id:14,publisher:'three'},
               {name:'ddd',id:15,publisher:'four'}
             ]
  }
]

I am not writing SQL query here but please assume similar kind of database schema. dbRow in following code is output of select query. Following code is working fine but I am getting all the books in one array, and I am not able to figure out how can I make it group by categories.

detailsMap := make(map[uint][]*details)
for dbRow.Next() {
  var det details
  detErr := dbRow.StructScan(&det)
  detailsMap[det.id] = append(detailsMap[det.id], &det)
}

score 0 · Answer 1 · answered Oct 13 '16 at 04:26

The #1 asked question on SO's go tag.

Struct members has to be exported, aka start with capital letter.

type book struct{
  Category string `json:"category"`
  Books []*BookDetails `json:"books"`
}

type BookDetails struct{
  Name  string `json:"name"`
  ID    uint `json:"id"`
  Publisher string `json:"publisher"`
}

golang nested struct and map

1 Answers1