sschmid/Entitas · error · EntityDoesNotHaveComponentException

Cannot get component

Error message

Cannot get component '{_contextInfo.ComponentNames[index]}' from {this}!

What it means

Thrown by Entity.GetComponent when the component at the given index does not exist on the entity. Reading a component in Entitas requires that it is present; there is no null-return contract, so a missing component is an exception.

Solutions

1. Use the generated has-check: if (entity.hasPosition) { var p = entity.position; }
2. Call entity.HasComponent(index) before GetComponent for raw-index access
3. Match the group on all components you intend to read (e.g. Matcher.AllOf(...))
4. Restructure so removal happens after all readers processed the frame

Example fix

// before
var pos = entity.position; // throws when !hasPosition
// after
if (entity.hasPosition) {
    var pos = entity.position;
    // use pos
}

if (entity.HasComponent(index)) { var c = entity.GetComponent(index); }

bool TryGetComponent(Entity e, int index, out IComponent c) { c = e.HasComponent(index) ? e.GetComponent(index) : null; return c != null; }

try { var c = entity.GetComponent(index); }
catch (EntityDoesNotHaveComponentException) { c = null; }

When it happens

Trigger: Calling entity.GetComponent(index) or a generated e.position when entity.hasPosition is false; reading after RemoveComponent; reading in a system that matched a broader group than the component requires.

Common situations: Group matching on one component while reading another; ordering bugs where a removal system runs before the reader; typos confusing similar components.

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

• Cannot remove component
• Cannot replace component
• Cannot destroy !
• EntityIsAlreadyRetainedByOwnerException(_entity, owner)
• EntityIsNotRetainedByOwnerException(_entity, owner)

AI-assisted analysis of sschmid/Entitas@37547d1bd2 (2026-09-14). Data as JSON: /api/errors/d192d471de1015d5. Report an issue: GitHub.

Appendix: source

Thrown at src/Entitas/Entity/Entity.cs:215

                    OnComponentRemoved?.Invoke(this, index, previousComponent);
                }

                GetComponentPool(index).Push(previousComponent);
            }
            else
            {
                OnComponentReplaced?.Invoke(this, index, previousComponent, newComponent);
            }
        }

        /// Returns a component at the specified index.
        /// You can only get a component at an index if it exists.
        /// The preferred way is to use the
        /// generated methods from the code generator.
        public IComponent GetComponent(int index)
        {
            if (!HasComponent(index))
                throw new EntityDoesNotHaveComponentException(index,
                    $"Cannot get component '{_contextInfo.ComponentNames[index]}' from {this}!",
                    "You should check if an entity has the component before getting it.");

            return _components[index];
        }

        /// Returns all added components.
        public IComponent[] GetComponents()
        {
            if (_componentsCache == null)
            {
                for (var i = 0; i < _components.Length; i++)
                {
                    var component = _components[i];
                    if (component != null)
                        _componentBuffer.Add(component);
                }

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