访问嵌套结构中的字段

Question

How do I reference a field in the "AllData" struct below from the main "Forecast" struct? e.g if I wanted to reference "TemperatureMax from Forecast -> Daily?

type AllData struct {
    Time                       float64 `json:"time"`
    Summary                    string  `json:"summary"`
    Icon                       string  `json:"icon"`
    TemperatureMin             float64 `json:"temperatureMin"`
    TemperatureMinTime         float64 `json:"temperatureMinTime"`
    TemperatureMax             float64 `json:"temperatureMax"`
}

type HourlyData struct {
    Summary string        `json:"summary"`
    Icon    string        `json:"icon"`
    Data    []CurrentData `json:"data"`
}

type DailyData struct {
    Summary string    `json:"summary"`
    Icon    string    `json:"icon"`
    Data    []AllData `json:"data"`
}

type Forecast struct {
    Latitude  float64     `json:"latitude"`
    Longitude float64     `json:"longitude"`
    Timezone  string      `json:"timezone"`
    Offset    int         `json:"offset"`
    Currently CurrentData `json:"currently"`
    Hourly    HourlyData  `json:"hourly"`
    Daily     DailyData   `json:"daily"`
    Flags     Flags       `json:"flags"`
}

Answer 1

You can access an AllData field from a Forecast struct by providing an index into the Data slice in DailyData. Consider this stripped-down example of your question:

package main

import "fmt"

type AllData struct {
    Summary string
}

type DailyData struct {
    Data []AllData
}

type Forecast struct {
    Daily DailyData
}

func main() {
    a := AllData{"summary"}
    s := []AllData{a}
    d := DailyData{s}
    f := Forecast{d}

    val := f.Daily.Data[0].Summary

    fmt.Println(val)
}

In main, we read the Summary field from the AllData struct at index 0 of the DailyData's Data slice. This prints summary to the console.

Optionally, we could access multiple AllData structs by ranging over the slice in DailyData:

func main() {
    a1 := AllData{"summary1"}
    a2 := AllData{"summary2"}
    a3 := AllData{"hello"}
    s := []AllData{a1, a2, a3}
    d := DailyData{s}
    f := Forecast{d}

    for _, val := range f.Daily.Data {
        fmt.Println(val.Summary)
    }
}

The above prints:

summary1
summary2
hello