What is the difference between mapped interface {} and type structure {}?

Question content

I just read that map[Type]interface{} specifies the mapping of keys of Type type, and its value is any, that is interface{}.

Isn't this almost the same as defining a structure, that is, type Name struct{ key1; value1, ...., keyn: valuen}?

What is the difference between these two types of mapping?

I read https://www.digitalocean.com/community/tutorials/how-to-use-json-in-go but I still don't understand the difference.

Or what is the difference between map[type] interface{} which we define in a more general way?

We define each key-value pair through the structure?

Are these two methods just defining objects composed of key-value pairs?

Correct answer

Structure and mapping are different data structures. They have many differences. Here are just a few:

A structure has a fixed number of fields, which are declared once and cannot be changed.

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The map can grow or shrink at runtime.

vector := map[string]float64{
    "x": 2.0,
    "y": 2.0,
}

vector["z"] = 2.0

You can loop through map entries.

for key, val := range vector {
    fmt.Println(key, val)
}

Structures do not support iteration (unless you use reflection).

Structure fields can have labels (additional attributes):

type User struct {
    Name          string    `json:"name"`
    Password      string    `json:"password"`
}

The map does not have this function.

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