How to Efficiently Retrieve Values from Deeply Nested Maps in Go?

Retrieving Values from Nested Maps

In Go, navigating and retrieving values from deeply nested maps can be a challenge. This question demonstrates how to effectively accomplish this task.

Question

How can I access and retrieve values from a nested map with a structure like this:

m := map[string]interface{}{
    "date":       "created",
    "clientName": "data.user.name",
    "address": map[string]interface{}{
        "street": "x.address",
    },
    "other": map[string]interface{}{
        "google": map[string]interface{}{
            "value": map[string]interface{}{
                "x": "y.address",
            },
        },
    },
    "new_address": map[string]interface{}{
        "address": "z.address",
    },
}

Answer

To retrieve values from nested maps, you can employ the technique of nonpanic casting, which involves the following steps:

for i := range m {
    nestedMap, ok := m[i].(map[string]interface{})
    if ok {
        // Do what you want
    }
}

In the provided example, the code iterates over the top-level keys of the map m. For each key, it attempts to cast the corresponding value to a map[string]interface{}, checking if the type assertion is successful using the boolean flag ok. If the type assertion is successful, you can then access and manipulate the nested map as needed.

For further details on type assertions in Go, refer to the official documentation at https://golang.org/ref/spec#Type_assertions. This approach allows you to navigate and retrieve values from nested maps in a convenient and error-free manner.

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