Safely Handling Arbitrary Data

We have a utility that processes its command-line arguments; if everything goes as expected, then we get the supported types of command-line arguments, and everything goes smoothly. But what happens when something unexpected occurs? In that case, the map[string]interface{} map is here to help, and this lesson shows how!

Rationale for map[string]interface{}

Remember that the biggest advantage we get from using a map[string]interface{} map, or any map that stores an interface{} value, in general, is that we still have our data in its original state and data type. If we use map[string]string instead, or anything similar, then any data we have is going to be converted into a string, which means that we are going to lose information about the original data type and the structure of the data we are storing in the map.

How map[string]interface{} works

Nowadays, web services work by exchanging JSON records. If we get a JSON record in a supported format, then we can process it as expected, and everything will be fine. However, there are times when we might get an erroneous record or a record in an unsupported JSON format. In these cases, using map[string]interface{} for storing these unknown JSON records (arbitrary data) is a good choice because map[string]interface{} is good at storing JSON records of an unknown type.

Coding example

We are going to illustrate this technique using a utility named mapEmpty.go that processes arbitrary JSON records given as command-line arguments. We process the input JSON record in two ways that are similar but not identical. There is no real difference between the exploreMap(), and typeSwitch() functions apart from the fact that typeSwitch() generates a much richer output. The code of mapEmpty.go is as follows: