改进多图访问，避免错误的类型转换

Question

I have this code in my project:

//data.Objects is a map[string]interface{}
corporateName := data.Objects["corporateName"].(string)
dba := data.Objects["dba"].(string)
licence := data.Objects["licence"].(string)
resaleCert := data.Objects["resaleCert"].(string)
einNumber := data.Objects["einNumber"].(string)
phoneNumber := data.Objects["phoneNumber"].(string)
website := data.Objects["website"].(string)
contactName := data.Objects["contactName"].(string)
email := data.Objects["email"].(string)
billingAddress := data.Objects["billingStreet"].(string)
billingCity := data.Objects["billingCity"].(string)
billingCode := data.Objects["billingCode"].(int64)
billingState := data.Objects["billingState"].(string)
billingCountry := data.Objects["billingContry"].(string)
deliveryAddress := data.Objects["deliveryAddress"].(string)

In the declared map, some of these key couldn't have a value associated so they can return nil. If they do that I'm not able to do a type conversion. I'm looking for a way in order to improve this access and prevent the incorrect conversion.

Using some if else to check it it's quite annoying and verbose. Is there a way in order to avoid it?

N.B. The nil values for the structure are perfectly legal in this case so it's not a problem that I can avoid before.

Answer 1

As @JimB mentions you can use a custom type, e.g.

type detailsMap map[string]interface{}

func (dm detailsMap) String(key string) string {
    if val, ok := dm[key].(string); ok {
        return val
    }
    return ""
}

func (dm detailsMap) Int64(key string) int64 {
    if val, ok := dm[key].(int64); ok {
        return val
    }
    return 0
}

Note that default zero values are returned if the desired key is not present in the type's underlying map[string]interface{}.

If you haven't got control of the original data.Objects then you can convert it to a detailsMap via detailsMap(data.Objects).

You can then get values out as follows:

corporateName := dm.String("corporateName")
website := dm.String("website")
billingCode := dm.Int64("billingCode")

Here's an example on the playground.