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district.go
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district.go
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package myschoollist
import (
"encoding/json"
"os"
"path/filepath"
)
// District - information about a district and mapping to district
type District struct {
ID int `json:"id"`
Name string `json:"name"`
StateID int `json:"state_id"` // references the state this district is in
}
// districts - slice of districts in Malaysia and important mappings
type districts struct {
items []District
mapDistrictsID map[int]int
mapDistrictsState map[int][]int
}
// newDistricts - creates new instance of Districts with proper mapping
func newDistricts(jsonDir string) (districtsV *districts, err error) {
districtsV = new(districts)
file, err := os.Open(filepath.Join(jsonDir, "district.json"))
if err != nil {
return
}
defer file.Close()
err = json.NewDecoder(file).Decode(&districtsV.items)
if nil != err {
return
}
districtsV.mapDistrictsID = make(map[int]int)
districtsV.mapDistrictsState = make(map[int][]int)
// we map the slice index to a map for quicker access intead of looping through the slice one by one
for index, district := range districtsV.items {
districtsV.mapDistrictsID[district.ID] = index
districtsV.mapDistrictsState[district.StateID] = append(districtsV.mapDistrictsState[district.StateID], district.ID)
}
return
}
// GetByID - returns district information given its id
func (districts *districts) GetByID(id int) (district District, found bool) {
index, found := districts.mapDistrictsID[id]
if !found {
return
}
district = districts.items[index]
return
}