runtime error: hash of unhashable type map[string]interface {}

[mateors]

Unable to perform group by query on the following dataset

rows := []map[string]interface{}{
	{"name": "Mostain", "salary": 30000, "ShipmentTag": "b001"},
	{"name": "Sanzida", "salary": 20000, "ShipmentTag": "b001"},
	{"name": "Riaz", "salary": 21000, "ShipmentTag": "b002"},
	{"name": "Pallobi", "salary": 30000, "ShipmentTag": "b001"},
	{"name": "Moaz", "salary": 20000, "ShipmentTag": "b001"},
	{"name": "Tareq", "salary": 21000, "ShipmentTag": "b002"},
}

	data := From(rows).Where(func(c interface{}) bool {
		cmap := c.(map[string]interface{})
		return len(cmap["name"].(string)) > 0

	}).GroupBy(func(ShipmentTag interface{}) interface{} {
		return ShipmentTag

	}, func(ShipmentTag interface{}) interface{} {
		return ShipmentTag

	}).First()

	fmt.Println(data)

Error details:

goroutine 1 [running]:
github.com/ahmetb/go-linq/v3.Query.GroupBy.func1()
E:/GOLANG/pkg/mod/github.com/ahmetb/go-linq/v3@v3.2.0/groupby.go:21 +0x15f
github.com/ahmetb/go-linq/v3.Query.First({0x5f0aa0?})
E:/GOLANG/pkg/mod/github.com/ahmetb/go-linq/v3@v3.2.0/result.go:188 +0x1a
main.main()

[kalaninja]

Hi @mateors. You are probably doing something wrong. You do a GroupBy over a list of maps. So in your keySelector function ShipmentTag is a map - not a "ShipmentTag" key.
The thing that you probably want to do is:

	data := From(rows).Where(func(c interface{}) bool {
		cmap := c.(map[string]interface{})
		return len(cmap["name"].(string)) > 0

	}).GroupBy(func(c interface{}) interface{} {
		cmap := c.(map[string]interface{})
		return cmap["ShipmentTag"]

	}, func(ShipmentTag interface{}) interface{} {
		return ShipmentTag

	}).First()

[mateors]

@kalaninja Thank you very much, It works, But I am wondering How can I use ToMap() instead of First()
Could you please show me an example?

[kalaninja]

@mateors

result := make(map[string]interface{})

From(rows).WhereT(func(x map[string]interface{}) bool {
	return len(x["name"].(string)) > 0
}).GroupByT(
	func(x map[string]interface{}) interface{} {
		return x["ShipmentTag"]
	},
	func(x interface{}) interface{} {
		return x
	},
).ToMapBy(&result,
	func(i interface{}) interface{} {
		return i.(Group).Key
	}, func(i interface{}) interface{} {
		return i.(Group).Group
	})

[mateors]

@kalaninja Thank you very much, you are superb! I noticed you used GroupByT but I want to use GroupBy only, no generics. I am concern about performance.

	result := make(map[string]interface{})

	data := From(rows).Where(func(c interface{}) bool {
		cmap := c.(map[string]interface{})
		return len(cmap["name"].(string)) > 0

	}).GroupBy(func(c interface{}) interface{} {
		cmap := c.(map[string]interface{})
		return cmap["ShipmentTag"]

	}, func(ShipmentTag interface{}) interface{} {
		return ShipmentTag

	}).ToMapBy(&result,
		func(i interface{}) interface{} {
			return i.(Group).Key
		}, func(i interface{}) interface{} {
			return i.(Group).Group
		})

above code not working.
It says (no value) used as value

[kalaninja]

that is probably because you are trying to read the resulting data from data instead of result?
ToMapBy doesn't return a value, it populates a map you provide instead.

[mateors]

@kalaninja No its compiling error, code seems okay but I don't know why not showing error. Could you please compile at your end? Advance thanks for your kind quick response.

[kalaninja]

@mateors I think the reason might be because ToMapBy doesn't return any value. Can you try removing data := from your code please?

[mateors]

@kalaninja Thank you, following code working now. Jajakallah. You make my day. I am fasting as we are celebrating Ramadan, I pray for your success.

	result := make(map[string]interface{})

	From(rows).Where(func(c interface{}) bool {
		cmap := c.(map[string]interface{})
		return len(cmap["name"].(string)) > 0

	}).GroupBy(func(c interface{}) interface{} {
		cmap := c.(map[string]interface{})
		return cmap["ShipmentTag"]

	}, func(ShipmentTag interface{}) interface{} {
		return ShipmentTag

	}).ToMapBy(&result,
		func(i interface{}) interface{} {
			return i.(Group).Key
		}, func(i interface{}) interface{} {
			return i.(Group).Group
		})

	fmt.Println(result)

[kalaninja]

I was glad to help @mateors. Welcome. And happy celebration.