英文:
Initializing a struct in a struct
问题
这是类似帖子的一个小变化。
我有一个名为data的包，其中包含以下内容：
type CityCoords struct {
Name string
Lat float64
Long float64
}
type Country struct {
Name string
Capitol *CityCoords
}
在我的主函数中，我尝试这样初始化一个Country：
germany := data.Country {
Name: "Germany",
Capitol: {
Name: "Berlin", // 错误出现在这一行
Lat: 52.5200,
Long: 13.4050,
},
}
当我构建项目时，我得到了与我上面标记的"Name"属性对齐的错误：
missing type in composite literal
如何解决这个错误？
英文:
This is a slight twist on similar posts.
I have a package called data that has the following:
type CityCoords struct {
Name string
Lat float64
Long float64
}
type Country struct {
Name string
Capitol *CityCoords
}
In my main function I try initializing a Country like so:
germany := data.Country {
Name: "Germany",
Capitol: {
Name: "Berlin", //error is on this line
Lat: 52.5200,
Long: 13.4050,
},
}
When I build my project, I get this error aligned with the "Name" attributed as I've flagged above:
missing type in composite literal
How do I resolve this error?
答案1
得分: 3
据我所知，*表示期望一个对象指针。所以，你可以使用&先初始化它；
func main() {
germany := &data.Country{
Name: "Germany",
Capitol: &data.CityCoords{
Name: "Berlin", //错误出现在这一行
Lat: 52.5200,
Long: 13.4050,
},
}
fmt.Printf("%#v\n", germany)
}
或者，你可以选择一种更优雅的方式；
// data.go
package data
type Country struct {
Name string
Capital *CountryCapital
}
type CountryCapital struct {
Name string
Lat float64
Lon float64
}
func NewCountry(name string, capital *CountryCapital) *Country {
// 注意：所有属性必须在相同的范围内
return &Country{name, capital}
}
func NewCountryCapital(name string, lat, lon float64) *CountryCapital {
// 注意：所有属性必须在相同的范围内
return &CountryCapital{name, lat, lon}
}
// main.go
func main() {
c := data.NewCountry("Germany", data.NewCountryCapital("Berlin", 52.5200, 13.4050))
fmt.Printf("%#v\n", c)
}
以上是翻译好的内容。
英文:
As far as know, * means that an object pointer is expected. So, you could initiate it first using &;
func main() {
germany := &data.Country{
Name: "Germany",
Capitol: &data.CityCoords{
Name: "Berlin", //error is on this line
Lat: 52.5200,
Long: 13.4050,
},
}
fmt.Printf("%#v\n", germany)
}
Or, you can prefer a more elegant way;
// data.go
package data
type Country struct {
Name string
Capital *CountryCapital
}
type CountryCapital struct {
Name string
Lat float64
Lon float64
}
func NewCountry(name string, capital *CountryCapital) *Country {
// note: all properties must be in the same range
return &Country{name, capital}
}
func NewCountryCapital(name string, lat, lon float64) *CountryCapital {
// note: all properties must be in the same range
return &CountryCapital{name, lat, lon}
}
// main.go
func main() {
c := data.NewCountry("Germany", data.NewCountryCapital("Berlin", 52.5200, 13.4050))
fmt.Printf("%#v\n", c)
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论