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In this video, we'll connect the toggleConfirmationAt function to the Guest component.
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In the last video we wrote a method
called toggleConfirmationAt that took
0:00
an index as an argument,
then it found the corresponding array and
0:04
the state and flipped the Boolean
corresponding guest confirmed status.
0:09
So lets pass the toggleConfirmationAt
method down to the Guest component and
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bind it to the check box's change event,
so I'll scroll down to the GuestList
0:18
component, And I'll pass it a new
prop called toggleConfirmationAt,
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And I'll pass it the function
with this.toggleConfirmationAt.
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Now I'll open up the GuestList component
and add our new prop to the propTypes.
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Let's say toggleConfirmationAt:,
PropTypes.func.isRequired.
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Then in the Guest component
I'm going to add a new prop,
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let's call it handleConfirmation.
1:00
And we really want the
toggleConfirmationAt function to be called
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when the check box is changed
on the guest component.
1:10
But because the change event takes
place in the guest component
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We'll need to pass this handle down
through the guest component's props.
1:16
Now our handler requires an index.
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Remember, individual guest components
are unaware of any other guest in the app,
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much less their position
in the state's guest array.
1:28
So the knowledge of a guest
position is in this component,
1:30
GuestList and it's available
from the index variable here.
1:35
So as the value for
handle confirmation.We'll create
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a new function that will
call toggle confirmation at
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with props.toggleConfirmationAt(index).
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Remember in JavaScript functions remember
the scope in which they are declared.
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So even though this function
will be passed down and
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called inside the guest component it
will remember the value of index and
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pass it into toggleConfirmationAt
this is known as a closure.
2:08
And if you're unfamiliar with this concept
or need a refresher I recommend checking
2:12
the teachers notes for resources
closures come up often and React.
2:16
All right now that our handler is
available in the guest component
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let's open up Guest.js and
edit to the propTypes.
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Say handleConfirmation,
PropTypes.funcisRequired.
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And now we can bind it to
the checkbox's change event.
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So, in the input, say onChange,
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Pprops.handleConfirmation.
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So when the change event occurs, this
function will receive an event object.
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Over in GuestList, the function we
created here would receive that
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object if we added a parameter here for
example, event.
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Now we might need this event if we
wanted the value from this input but
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since we know we're just going to
flip the isConfirm property for
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this guest we don't need to
pass that back to the tree.
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Now you might be thinking that when the
user clicks this box it visibly changes,
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and then passes that information
to the state or the handler.
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Well, it's a slightly different sequence.
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You see, the check box's state is being
managed by the app component's state.
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So it only visibly changes
when that state changes.
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So the information is making a loop or
a circuit.
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When changes are made to the UI,
the state changes in response.
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Changes in the state, then,
result in changes to the UI.
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So when we look at our app in the browser,
you can see that when I click on
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the check boxes, they change and
that's what we were hoping for.
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I can even open up the React dev tools and
unfold the state object and
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you can see the state is changing to
reflect what we're seeing on the page.
4:10
So isConfirmed changes from true to false.
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Great.
4:26
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