Elixir best practices - avoid creating unnecessary objects Page

Item 6: Elixir Best Practices - Avoid creating unnecessary objects

Introduction to Avoiding Unnecessary Object Creation in Elixir

Elixir is a dynamic, functional language designed for building scalable and maintainable applications. While Elixir is known for its efficient memory management, creating unnecessary objects can lead to increased memory usage, reduced performance, and potential bottlenecks, especially in high-throughput applications. By following best practices to avoid creating unnecessary objects, you can optimize your Elixir applications for better performance and efficiency.

Why Avoid Creating Unnecessary Objects in Elixir?

Avoiding unnecessary object creation in Elixir offers several important benefits:
1. **Reducing Memory Usage**: By minimizing the creation of objects, you reduce the overall memory footprint of your application.
2. **Improving Performance**: Fewer objects mean less garbage collection, leading to improved application performance and lower latency.
3. **Enhancing Code Efficiency**: Writing code that avoids unnecessary object creation can make your application more efficient and scalable.

Example 1: Reuse Data Structures Where Possible

### Creating Unnecessary Lists (Anti-Pattern)

```elixir
def create_list do
list = Enum.to_list(1..10)
Enum.map(list, fn x -> x * 2 end)
end
```

In this example, a list is created and then immediately mapped over to produce a new list. This approach creates an intermediate list that is unnecessary if we only care about the final result.

### Reusing Data Structures

```elixir
def create_list do
1..10
|> Enum.map(&(&1 * 2))
end
```

In this improved version, the `Enum.map/2` function directly operates on the range, eliminating the need for an intermediate list and reducing memory usage.

Example 2: Avoid Repeatedly Creating Identical Objects

### Repeatedly Creating Identical Maps (Anti-Pattern)

```elixir
def process_data(data) do
Enum.map(data, fn item ->
map = %{key: "value", another_key: "another_value"}
Map.put(map, :item, item)
end)
end
```

In this example, the same map is created repeatedly within the `Enum.map/2` function, which is unnecessary and inefficient.

### Creating the Map Once

```elixir
def process_data(data) do
base_map = %{key: "value", another_key: "another_value"}

Enum.map(data, fn item ->
Map.put(base_map, :item, item)
end)
end
```

In this improved version, the map is created once outside the loop and reused, reducing unnecessary object creation.

Example 3: Use Pattern Matching Instead of Map Lookup

### Unnecessary Map Lookup (Anti-Pattern)

```elixir
def handle_event(event) do
case Map.get(event, :type) do
"start" -> handle_start(event)
"stop" -> handle_stop(event)
_ -> handle_unknown(event)
end
end
```

In this example, `Map.get/2` is used to retrieve the value associated with the `:type` key, which could be avoided by using pattern matching.

### Using Pattern Matching

```elixir
def handle_event(%{type: "start"} = event), do: handle_start(event)
def handle_event(%{type: "stop"} = event), do: handle_stop(event)
def handle_event(event), do: handle_unknown(event)
```

In this improved version, pattern matching is used directly in the function head, avoiding the need to create a new object to store the result of the map lookup.

Example 4: Prefer Immutability to Recreating Objects

In Elixir, data structures are immutable, but sometimes developers may inadvertently create new objects instead of reusing existing ones.

### Recreating Objects Unnecessarily (Anti-Pattern)

```elixir
def update_value(map) do
new_map = Map.put(map, :key, "new_value")
new_map
end
```

In this example, the map is unnecessarily reassigned to a new variable, which is redundant.

### Reusing Existing Objects

```elixir
def update_value(map) do
Map.put(map, :key, "new_value")
end
```

In this improved version, the result of `Map.put/3` is returned directly, avoiding the creation of an unnecessary variable.

When to Avoid Creating Unnecessary Objects in Elixir

Avoid creating unnecessary objects in the following scenarios:
- **Within Loops**: Avoid creating new objects inside loops or recursive functions unless necessary. Reuse existing data structures where possible.
- **When Pattern Matching**: Leverage pattern matching in function heads to avoid unnecessary lookups or object creation.
- **With Immutable Data**: Embrace Elixir's immutability by modifying data directly rather than creating new variables to hold the modified data.

Conclusion

In Elixir, avoiding unnecessary object creation is a best practice that helps reduce memory usage, improve performance, and enhance code efficiency. By reusing data structures, leveraging pattern matching, and embracing immutability, you can write more efficient and scalable Elixir applications.