# Add Components
An entity can have any number of components but only one in each storage.
Adding another component of the same type will replace the existing one.
## World
```rust, noplaypen
{{#include ../../../../tests/book/add_components.rs:world}}
```
⚠️ We have to use a single element tuple `(T,)` to add a single component.
## View
You'll notice that we use [`EntitiesView`](https://docs.rs/shipyard/latest/shipyard/struct.EntitiesView.html) and not [`EntitiesViewMut`](https://docs.rs/shipyard/latest/shipyard/struct.EntitiesViewMut.html) to add components.
The entities storage is only used to check if the [`EntityId`](https://docs.rs/shipyard/latest/shipyard/struct.EntityId.html) is alive.
We could of course use [`EntitiesViewMut`](https://docs.rs/shipyard/latest/shipyard/struct.EntitiesViewMut.html), but exclusive access is not necessary.
If you don't need or want to check if the entity is alive, you can use the [`AddComponent::add_component_unchecked`](https://docs.rs/shipyard/latest/shipyard/trait.AddComponent.html).
```rust, noplaypen
{{#include ../../../../tests/book/add_components.rs:view}}
```