为什么传递的变量没有在 html/template 中呈现？

Question

我不明白为什么传递的变量没有用 html/template 渲染

这是浏览器中呈现的内容：

这是所有传递的变量： [0xc0000a8ec0 0xc0000a8f80 0xc0000a9040 0xc0000a9100]

城市 人口 州 国家 首都

这是日志：

$ go run main.go

2019/11/27 11:00:39 **** => &city has &main.City{Name:"Washington D.C.", State:"", Country:"USA", Capital:false, Population:680000} before appending to cities ****

2019/11/27 11:00:39 **** => &city has &main.City{Name:"Los Angeles", State:"CA", Country:"USA", Capital:false, Population:3900000} before appending to cities ****

2019/11/27 11:00:39 **** => &city has &main.City{Name:"San Francisco", State:"CA", Country:"USA", Capital:false, Population:860000} before appending to cities ****

2019/11/27 11:00:39 **** => &city has &main.City{Name:"Tokyo", State:"", Country:"Japan", Capital:true, Population:9000000} before appending to cities ****

**** => cities outside {} has 4

这是处理函数：

func indexHandler(w http.ResponseWriter, r *http.Request) {

    projectID := "XXXXXXXXXXXXXX"

    ctx := context.Background()

    client, _ := firestore.NewClient(ctx, projectID)

    query := client.Collection("cities").Documents(ctx)

    defer query.Stop()

    cities := make([]*City, 0)

    for {

        doc, err := query.Next()

        if err == iterator.Done {

            break

        }

        c := doc.Data()

        // is there an easier way to populate the city struct

        city := City{

            Name:       c["name"].(string),

            Country:    c["country"].(string),

            Population: c["population"].(int64),

        }

        // This is my ugly solution to dealing with nil value from Firestore

        _, ok := c["capital"]

        if ok {

            city.Capital = c["capital"].(bool)

        }

        state, ok := c["state"].(string)

        if ok {

            city.State = state

        }

        log.Printf("**** => &city has %#v before appending to cities ****", &city)

        cities = append(cities, &city)

    }

    fmt.Printf("**** => cities outside {} has %d", len(cities))

    indexTemplate.Execute(w, cities)    

}

Answer 1

永远不要遗漏错误，检查indexTemplate.Execute(w, cities)返回的内容。它可能揭示了原因：您cities作为数据传递，这是一个切片。没有cities它的领域或方法。传递的数据成为点，因此您必须在点上进行范围。代替：{{ range .cities }}使用：{{ range . }}