How to Access Data Inside Map In Elixir?

To access data inside a map in Elixir, you can use the dot notation or the square bracket notation.

Using the dot notation, you can access the value of a key in a map by specifying the key directly after the map variable followed by a dot. For example, if you have a map variable called my_map and you want to access the value of the key :name, you can do so by typing my_map.name.

Alternatively, you can also use the square bracket notation to access data inside a map. This involves specifying the key inside square brackets after the map variable. For example, to access the value of the key :age in the map my_map, you can do so by typing my_map[:age].

Both of these methods allow you to access data inside a map in Elixir.

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What is the size of an empty map in Elixir?

The size of an empty map in Elixir is 0. This is because an empty map does not contain any key-value pairs, so its size is 0.

How to convert a keyword list to a map in Elixir?

One way to convert a keyword list to a map in Elixir is to use the Enum.into/2 function along with the Map.new/1 function. Here is an example of how you can do this:

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keyword_list = [{:key1, "value1"}, {:key2, "value2"}, {:key3, "value3"}]

keyword_map = Enum.into(keyword_list, %{})

IO.inspect(keyword_map)

In this example, the keyword_list variable contains a list of tuples where the first element is the key and the second element is the value. We then use the Enum.into/2 function to convert this list into a map by passing in an empty map %{} as the second argument. This will transform the keyword list into a map with the keys and values from the original list.

You can run this code in an interactive Elixir shell to see the resulting map.

How to recursively update values in a nested map in Elixir?

One way to recursively update values in a nested map in Elixir is to use a recursive function that traverses the map and updates values as needed. Here's an example implementation:

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defmodule NestedMapUpdater do
  def update_nested_map(map, key, value) do
    Map.update!(map, key, fn
      submap when is_map(submap) -> update_nested_map(submap, key, value)
      _ -> value
    end)
  end
end

# Example usage
nested_map = %{
  key1: %{
    key2: %{
      key3: "old value"
    }
  }
}

updated_map = NestedMapUpdater.update_nested_map(nested_map, :key3, "new value")
IO.inspect(updated_map)

In this example, the update_nested_map/3 function takes a map, a key, and a value to update at that key. It recursively traverses the map and updates the value at the specified key. The function uses Map.update!/3 to conditionally update values depending on whether they are maps or not.

You can extend this function to handle more complex nested structures or different update conditions as needed.

What is the difference between a struct and a map in Elixir?

In Elixir, a struct and a map are both data structures that can be used to store and manipulate collections of key-value pairs. However, there are some key differences between the two:

1. Struct: A struct is a specific data type in Elixir that is defined using the defstruct macro. It allows you to define a named collection of fields with default values and specific types. Structs are often used to represent structured data and enforce a specific shape on the data. For example:

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defmodule Person do
  defstruct name: nil, age: 0
end

person = %Person{name: "John", age: 30}

1. Map: A map is a general-purpose data structure in Elixir that allows you to store key-value pairs where keys can be any data type. Maps do not enforce a specific structure or type on the data, which makes them more flexible than structs. Maps can be created using the %{} syntax. For example:

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person = %{name: "John", age: 30}

In summary, structs are used when you want to define a specific data structure with named fields and enforce a specific shape on the data, while maps are used when you need a more flexible and general-purpose data structure for storing key-value pairs.

How to extract keys from a map in Elixir?

In Elixir, you can extract keys from a map using the Map.keys/1 function. Here's an example:

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map = %{"name" => "Alice", "age" => 30, "city" => "New York"}
keys = Map.keys(map)
IO.inspect(keys)

This will output:

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["name", "age", "city"]

Alternatively, you can use the Enum.map/2 function with the Kernel.elem/2 function to extract keys:

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map = %{"name" => "Alice", "age" => 30, "city" => "New York"}
keys = Enum.map(map, &elem(&1, 0))
IO.inspect(keys)

This will also output:

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["name", "age", "city"]