Inline Method

Before you begin: Methods, arguments, and return values.

Inline Method replaces a method call with the called method’s body. Once all relevant callers have been updated, the unnecessary method can be removed. It is the reverse of Extract Method. 1

Original version: follow a call to discover the same idea

A reward combines a base amount and a bonus. One helper adds another name but no distinct rule.

public static class Rewards
{
    public static int Total(int baseAmount, int bonus)
    {
        return ComputeTotal(baseAmount, bonus);
    }

    private static int ComputeTotal(int baseAmount, int bonus)
    {
        return baseAmount + bonus;
    }
}

Total and ComputeTotal both name the same operation. The private helper has no other caller or independently useful responsibility in this example.

def _compute_total(base_amount, bonus):
    return base_amount + bonus


def total_reward(base_amount, bonus):
    return _compute_total(base_amount, bonus)

Reading total_reward sends us to _compute_total, which contains only the addition. Nothing else uses the helper in this example.

Refactored version: put the addition where it is used

public static class Rewards
{
    public static int Total(int baseAmount, int bonus)
    {
        return baseAmount + bonus;
    }
}

Rewards.Total(10, 5) still returns 15. The public method and its parameters remain; only the private forwarding step disappears.

def total_reward(base_amount, bonus):
    return base_amount + bonus

total_reward(10, 5) still returns 15. The public function remains; the internal forwarding step disappears.

Short is not the same as unnecessary

A one-line method can encode valuable knowledge. A method named QualifiesForFreeShipping may tell a reader far more than the comparison inside it. Inlining such a method everywhere can duplicate a business rule and make changes harder.

Also check for overridden methods, public API consumers, decorators, logging, and argument evaluation. Substituting a body for a call is unsafe if it bypasses dynamic dispatch or evaluates a side-effecting argument more than once.

Use inlining when the method’s name and boundary no longer earn their place, or as an intermediate step before reorganizing code differently. The objective is fewer unnecessary detours, not the fewest possible methods.

Sources

Martin Fowler — Inline Function, also known as Inline Method.