[go-nuts] converting arbitrary map without reflection

Alex Howard

at Aug 29, 2014 at 1:41 pm

Obviously I could just store the whole interface but i need to range over
an arbitrary map

On Friday, 29 August 2014 15:36:31 UTC+2, Alex Howard wrote:

Been using angular with Go with much success but I need to know is there
any way to range over an arbitrary map?

I have my data map[string]*CustomData and want to send it to this function
without writing custom function for each data type.

func MapToJSObject(m map[string]interface) {

for a, b := range m {
j, err := json.Encode(b)
// serialise as JS object[a] = b
}

}

the golang.org people say that if i need to use reflection i'm doing
something wrong, please help

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Lars Seipel

at Aug 30, 2014 at 1:45 pm

⇧

On Fri, Aug 29, 2014 at 06:41:33AM -0700, Alex Howard wrote:
Obviously I could just store the whole interface but i need to range over
an arbitrary map

I don't think so. The values you want to take in your function must
have *something* in common, otherwise you wouldn't be able to do
anything meaningful with them. See if you can find that something and
extract it into a type. Change your function to take a value of this
type.

Also look through the standard library or other high-quality Go code to
see at what kind of solutions other people arrived.

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Rogerjd

at Aug 30, 2014 at 3:13 pm

⇧

https://groups.google.com/d/msg/golang-nuts/5PLkLjK3c6Y/M37bd5kB1SEJ
Then, range over each value in the map,
test that value in a type switch.
Hope that helps.
Roger

On Saturday, August 30, 2014 9:46:21 AM UTC-4, Lars Seipel wrote:

On Fri, Aug 29, 2014 at 06:41:33AM -0700, Alex Howard wrote:
Obviously I could just store the whole interface but i need to range over
an arbitrary map

I don't think so. The values you want to take in your function must
have *something* in common, otherwise you wouldn't be able to do
anything meaningful with them. See if you can find that something and
extract it into a type. Change your function to take a value of this
type.

Also look through the standard library or other high-quality Go code to
see at what kind of solutions other people arrived.

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Alex Howard

at Aug 30, 2014 at 3:42 pm

⇧

Thanks for the link, only got so far as the
http://godoc.org/github.com/mitchellh/mapstructure post so far

seems to be a great package for unmarshalling map[string]interface{} into a
struct with no fuss

On 30 August 2014 17:13, rogerjd wrote:

https://groups.google.com/d/msg/golang-nuts/5PLkLjK3c6Y/M37bd5kB1SEJ
Then, range over each value in the map,
test that value in a type switch.
Hope that helps.
Roger

On Saturday, August 30, 2014 9:46:21 AM UTC-4, Lars Seipel wrote:

On Fri, Aug 29, 2014 at 06:41:33AM -0700, Alex Howard wrote:
Obviously I could just store the whole interface but i need to range over
an arbitrary map

I don't think so. The values you want to take in your function must
have *something* in common, otherwise you wouldn't be able to do
anything meaningful with them. See if you can find that something and
extract it into a type. Change your function to take a value of this
type.

Also look through the standard library or other high-quality Go code to
see at what kind of solutions other people arrived.

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Dario Castañé

at Aug 30, 2014 at 3:52 pm

⇧

You can also use Mergo, my library for merging and un/marshalling
structs and maps: https://github.com/imdario/mergo

Regards,

Dario Castañé
https://github.com/imdario/

El 30/08/14 17:42, Alex Howard escribió:

Thanks for the link, only got so far as the
http://godoc.org/github.com/mitchellh/mapstructure post so far

seems to be a great package for unmarshalling map[string]interface{} into a
struct with no fuss

On 30 August 2014 17:13, rogerjd wrote:

https://groups.google.com/d/msg/golang-nuts/5PLkLjK3c6Y/M37bd5kB1SEJ
Then, range over each value in the map,
test that value in a type switch.
Hope that helps.
Roger

On Saturday, August 30, 2014 9:46:21 AM UTC-4, Lars Seipel wrote:

On Fri, Aug 29, 2014 at 06:41:33AM -0700, Alex Howard wrote:
Obviously I could just store the whole interface but i need to range over
an arbitrary map

I don't think so. The values you want to take in your function must
have *something* in common, otherwise you wouldn't be able to do
anything meaningful with them. See if you can find that something and
extract it into a type. Change your function to take a value of this
type.

Also look through the standard library or other high-quality Go code to
see at what kind of solutions other people arrived.

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Alex Howard

at Aug 30, 2014 at 4:32 pm

⇧

I could optimise a lot of my Bitcoin API response handling code with that
library thanks

On 30 August 2014 17:52, Dario Castañé wrote:

You can also use Mergo, my library for merging and un/marshalling
structs and maps: https://github.com/imdario/mergo

Regards,

Dario Castañé
https://github.com/imdario/

El 30/08/14 17:42, Alex Howard escribió:

Thanks for the link, only got so far as the
http://godoc.org/github.com/mitchellh/mapstructure post so far

seems to be a great package for unmarshalling map[string]interface{} into a
struct with no fuss

On 30 August 2014 17:13, rogerjd wrote:

https://groups.google.com/d/msg/golang-nuts/5PLkLjK3c6Y/M37bd5kB1SEJ
Then, range over each value in the map,
test that value in a type switch.
Hope that helps.
Roger

On Saturday, August 30, 2014 9:46:21 AM UTC-4, Lars Seipel wrote:

On Fri, Aug 29, 2014 at 06:41:33AM -0700, Alex Howard wrote:
Obviously I could just store the whole interface but i need to range over
an arbitrary map

I don't think so. The values you want to take in your function must
have *something* in common, otherwise you wouldn't be able to do
anything meaningful with them. See if you can find that something and
extract it into a type. Change your function to take a value of this
type.

Also look through the standard library or other high-quality Go code to
see at what kind of solutions other people arrived.

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Steve McCoy

at Aug 29, 2014 at 2:30 pm

⇧

I might be missing something, but why not json.Encode(m) ?

On Friday, August 29, 2014 9:36:31 AM UTC-4, Alex Howard wrote:

Been using angular with Go with much success but I need to know is there
any way to range over an arbitrary map?

I have my data map[string]*CustomData and want to send it to this function
without writing custom function for each data type.

func MapToJSObject(m map[string]interface) {

for a, b := range m {
j, err := json.Encode(b)
// serialise as JS object[a] = b
}

}

the golang.org people say that if i need to use reflection i'm doing
something wrong, please help

--
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To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscribe@googlegroups.com.
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Alex Howard

at Aug 29, 2014 at 3:15 pm

⇧

I could do that for sure, but this was research into whether or not it is
possible or not. I have concluded that it is impossible in go to do this
type of reflection whether in a type switch or with reflect package:

func SerializeEachRowSeparately(i interface{}) string {
resolved_map, ok := i.(reflect.TypeOf(i))
if !ok { return "FAILED" }
for a, b := range resolved_map { // do something to the row }
return ""
}

On Friday, 29 August 2014 16:30:06 UTC+2, Steve McCoy wrote:

I might be missing something, but why not json.Encode(m) ?

On Friday, August 29, 2014 9:36:31 AM UTC-4, Alex Howard wrote:

Been using angular with Go with much success but I need to know is there
any way to range over an arbitrary map?

I have my data map[string]*CustomData and want to send it to this
function without writing custom function for each data type.

func MapToJSObject(m map[string]interface) {

for a, b := range m {
j, err := json.Encode(b)
// serialise as JS object[a] = b
}

}

the golang.org people say that if i need to use reflection i'm doing
something wrong, please help

--
You received this message because you are subscribed to the Google Groups "golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscribe@googlegroups.com.
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Steve McCoy

at Aug 29, 2014 at 4:12 pm

⇧

It is possible. reflect.TypeOf(i) is not a compile-time construct, so you
can't use it in a type assertion. You have to use runtime constructs all
the way:

func LoopThroughAnyMap(i interface{}) {
     m := reflect.ValueOf(i)
     for _, k := range m.MapKeys() {
         v := m.MapIndex(k)
         i := v.Interface()
         // do something with i
     }
}

On Friday, August 29, 2014 11:15:28 AM UTC-4, Alex Howard wrote:

I could do that for sure, but this was research into whether or not it is
possible or not. I have concluded that it is impossible in go to do this
type of reflection whether in a type switch or with reflect package:

func SerializeEachRowSeparately(i interface{}) string {
resolved_map, ok := i.(reflect.TypeOf(i))
if !ok { return "FAILED" }
for a, b := range resolved_map { // do something to the row }
return ""
}

On Friday, 29 August 2014 16:30:06 UTC+2, Steve McCoy wrote:

I might be missing something, but why not json.Encode(m) ?

On Friday, August 29, 2014 9:36:31 AM UTC-4, Alex Howard wrote:

Been using angular with Go with much success but I need to know is there
any way to range over an arbitrary map?

I have my data map[string]*CustomData and want to send it to this
function without writing custom function for each data type.

func MapToJSObject(m map[string]interface) {

for a, b := range m {
j, err := json.Encode(b)
// serialise as JS object[a] = b
}

}

the golang.org people say that if i need to use reflection i'm doing
something wrong, please help

--
You received this message because you are subscribed to the Google Groups "golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

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Alex Howard

at Aug 29, 2014 at 9:20 pm

⇧

Thanks a lot this was driving me insane

On Friday, 29 August 2014 18:12:26 UTC+2, Steve McCoy wrote:

It is possible. reflect.TypeOf(i) is not a compile-time construct, so you
can't use it in a type assertion. You have to use runtime constructs all
the way:

func LoopThroughAnyMap(i interface{}) {
m := reflect.ValueOf(i)
for _, k := range m.MapKeys() {
v := m.MapIndex(k)
i := v.Interface()
// do something with i
}
}

On Friday, August 29, 2014 11:15:28 AM UTC-4, Alex Howard wrote:

I could do that for sure, but this was research into whether or not it is
possible or not. I have concluded that it is impossible in go to do this
type of reflection whether in a type switch or with reflect package:

func SerializeEachRowSeparately(i interface{}) string {
resolved_map, ok := i.(reflect.TypeOf(i))
if !ok { return "FAILED" }
for a, b := range resolved_map { // do something to the row }
return ""
}

On Friday, 29 August 2014 16:30:06 UTC+2, Steve McCoy wrote:

I might be missing something, but why not json.Encode(m) ?

On Friday, August 29, 2014 9:36:31 AM UTC-4, Alex Howard wrote:

Been using angular with Go with much success but I need to know is
there any way to range over an arbitrary map?

I have my data map[string]*CustomData and want to send it to this
function without writing custom function for each data type.

func MapToJSObject(m map[string]interface) {

for a, b := range m {
j, err := json.Encode(b)
// serialise as JS object[a] = b
}

}

the golang.org people say that if i need to use reflection i'm doing
something wrong, please help

--
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group	golang-nuts @
categories	go
posted	Aug 29, '14 at 1:36p
active	Aug 30, '14 at 4:32p
posts	11
users	5
website	golang.org

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[go-nuts] converting arbitrary map without reflection

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