segredo dos slots

This page assumes you've already read the Components Basics. Read that first if you are

new to components.

Slot Content and Outlet 鈥?/p>

We have learned that components can accept

props, which can be JavaScript values of any type. But how about template content? In

some cases, we may want to pass a template fragment to a child component, and let the

child component render the fragment within its own template.

For example, we may have a

component that supports usage like this:

template < FancyButton > Click

me!

The template of looks like

this:

template < button class = "fancy-btn" > < slot >

button >

The element is a slot outlet that indicates where the parent-provided

slot content should be rendered.

And the final rendered DOM:

html < button class =

"fancy-btn" >Click me!

With slots, the is responsible for

rendering the outer (and its fancy styling), while the inner content is

provided by the parent component.

Another way to understand slots is by comparing them

to JavaScript functions:

js // parent component passing slot content FancyButton (

'Click me!' ) // FancyButton renders slot content in its own template function

FancyButton ( slotContent ) { return `

R${ slotContent }

` }

Slot content is not just limited to text. It can be any valid template

content. For example, we can pass in multiple elements, or even other

components:

template < FancyButton > < span style = "color:red" >Click me! <

AwesomeIcon name = "plus" />

By using slots, our is more

flexible and reusable. We can now use it in different places with different inner

content, but all with the same fancy styling.

Vue components' slot mechanism is

inspired by the native Web Component element, but with additional capabilities

that we will see later.

Render Scope 鈥?/p>

Slot content has access to the data scope of the

parent component, because it is defined in the parent. For example:

template < span >{{

message }} < FancyButton >{{ message }}

Here both {{ message

}} interpolations will render the same content.

Slot content does not have access to

the child component's data. Expressions in Vue templates can only access the scope it

is defined in, consistent with JavaScript's lexical scoping. In other

words:

Expressions in the parent template only have access to the parent scope;

expressions in the child template only have access to the child scope.

Fallback Content

鈥?/p>

There are cases when it's useful to specify fallback (i.e. default) content for a

slot, to be rendered only when no content is provided. For example, in a

component:

template < button type = "submit" > < slot >

We might

want the text "Submit" to be rendered inside the if the parent didn't provide

any slot content. To make "Submit" the fallback content, we can place it in between the

tags:

template < button type = "submit" > < slot > Submit

Now when we use in a parent component,

providing no content for the slot:

template < SubmitButton />

This will render the

fallback content, "Submit":

html < button type = "submit" >Submit

But if we

provide content:

template < SubmitButton >Save

Then the provided

content will be rendered instead:

html < button type = "submit" >Save

Named

Slots 鈥?/p>

There are times when it's useful to have multiple slot outlets in a single

component. For example, in a component with the following

template:

template < div class = "container" > < header > < main > < footer >

For these cases, the

element has a special attribute, name , which can be used to assign a unique ID to

different slots so you can determine where content should be rendered:

template < div

class = "container" > < header > < slot name = "header" > < main >

< slot > < footer > < slot name = "footer" >

div >

A outlet without name implicitly has the name "default".

In a parent

component using , we need a way to pass multiple slot content fragments,

each targeting a different slot outlet. This is where named slots come in.

To pass a

named slot, we need to use a