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Okay so now we're going to talk
about conditional typings. So
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like we told you here, we don't
want a string, we want
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something that is either a
frost spell name or a fire
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spell name depending on the
type that we received here,
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okay? So if it's a fire spell,
we want the fire spell name.
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And the opposite as well. So
basically what we want okay so
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I'm going to write something
that doesn't make sense at all
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it's not like that that you're
going to write it but that's
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the idea basically we would like
this type for example to be
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conditionally something so
something like this for example
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if S extends fire spell so if
basically this is a fire spell
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then we want this type to be
fire spell name otherwise we
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want this type to be frost
spell name and obviously you
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cannot do it like this but you
can create a type out of that
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okay so when you want to write
a condition like this you can
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just take this create a type.
So for example I could create a
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type and not an interface and I
will explain right after why
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not an interface. So type that
could be spell name
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like this and so basically I
want to say that if S extend
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fairy spell then set fire
spell name otherwise set frost
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spell name but S doesn't exist
here so basically here it's
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like you're creating a function
so you have to receive this S
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as parameter okay this spell so
here I'm going to receive the
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spell like this and now I can
use my spell name and say that
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it's going to be of type of the
spell that I've received here.
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So this is basically this S is
basically a fire spell or a
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frost spell type. Okay and so
I'm going to send this type
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here and the condition is going
to be applied and it will
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return the correct type. So now
if I go here
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and try to send a fire spell
name here. for example big bang
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as you can see it's not working
anymore because Fire spell big
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bank is not assignable to frost
spell name so Typescript
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understood that since I have
sent a frost spell here and
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that my frost wizard is now of
type frostpell it has sent this
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frost spell as parameter right
here so this is a frost spell
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okay S is a frost spell so here
it has called spell name frost
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spell and here frost spell has
been sent this S is a frost
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spell and it does not extend
via spell so this is what has
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been returned okay so you can
do that with types okay and
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obviously this is an advanced
topic right but you can do that
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with type you could also do it
with interfaces but that would
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be less convenient because
there is another difference
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between types and interfaces
with a type I can do that
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example my string and say that
is a string for example but I
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cannot do that with an
interface okay with interface
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you always have to create an
extra attribute okay I would
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have to create for example name
and then string so you have to
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create another extra key why
with the type you can directly
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set a type without a key okay
without creating an object okay
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but I could do that here with an
interface I would just add an
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extra object here I would do
something like this and here I
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would receive my spell and this
would be spell name okay so
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this would work but here I
would have to call for example
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that spell name and in spell
name I would have my. name
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finally okay and so it wouldn't
work anymore here because here
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I would be forced to send a
name here and finally my frost
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spell name blizzard like this,
okay? So it's less convenient
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when you want to do a
conditional type. All right? So
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I will prefer to use type
approach like this.
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So don't worry this is a really
advanced topic but I hope it's
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clear and yeah we're good with
that so congratulation and see
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you in the next one.