6

I want to parse this JSON (in config/synch.conf):

{ "period" :"yy", "exec_period" : { "start" : { "month" : 1, "week" : 2, "day" : 3, "hour" : 4, "minute" : 5 }, "end" : { "month" : 6, "week" : 7, "day" : 8, "hour" : 9, "minute" : 10 } }, "backup" : [ { "local_dir" : "directoryLo1", "server_dir" : "directoryLo2", "server_host" : "domaineName" }, { "local_dir" : "directoryLo1", "server_dir" : "directorySe2", "server_host" : "domaineName" } ], "incremental_save" : "1Y2M" }

With this programm:

package main import ( "encoding/json" "fmt" "io/ioutil" ) func main() { content, err := ioutil.ReadFile("config/synch.conf") if err == nil { type date struct{ month float64 week float64 day float64 hour float64 minute float64 } type period struct{ start date end date } type backupType []struct{ local_dir string server_dir string server_host string } type jason struct{ period string exec_period period backup backupType incremental_save string } var parsedMap jason err := json.Unmarshal(content, &parsedMap) if err!= nil { fmt.Println(err) } fmt.Println(parsedMap) } else { panic(err) } }

Which doesn't work as expected, as the output is:

{ {{0 0 0 0 0} {0 0 0 0 0}} [] }

Here is the same example at play.golang.org
http://play.golang.org/p/XoMJIDIV59

I don't know if this is possible with go, but I wanted to get the value of the json.Unmarshal function stored in a map[string]interface{} (or another object that allows that) where I could access, for example, the value of the minute's end (10) like this: parsedMap["exec_period"]["end"]["minute"], but I don't uderstand the "Generic JSON withinterface{}" part of JSON and Go at golang.org

Improve this question

1 Answer 1

Reset to default
13

Your code is fine except that the json package can only work with exported fields.

Everything will work if you capitalize the first letter for each field name:

type date struct { Month float64 Week float64 Day float64 Hour float64 Minute float64 } type period struct { Start date End date } type backupType []struct { Local_dir string Server_dir string Server_host string } type jason struct { Period string Exec_period period Backup backupType Incremental_save string }

While it is possible to marshal into a map[string]interface{}, if the data has a set structure (such as the one in your question), your solution is most likely preferable. Using interface{} would require type assertions and might end up looking messy. Your example would look like this:

parsedMap["exec_period"].(map[string]interface{})["end"].(map[string]interface{})["minute"].(float64)
Improve this answer
Sign up to request clarification or add additional context in comments.

4 Comments

Really, was it that simple?! Thank you ANisus!
Now, my question is, how to access the value of the exec_period's minute's end? parsedMap["exec_period"]["end"]["minute"] doesn't work and replies invalid operation: parsedMap["exec_period"] (index of type jason), with first letters capitalized or not
To access the value, use parsedMap.Exec_period.End.Minute . Much cleaner than with interface type assertion! (as I added to the answer)
What if we have arbitrary data as JSON. We must use map[string]interface{}. Right? Could you give me an example of that?