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- Alright, I just wanna sum
up everything we just did

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in this composition around design,

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and just kind of hear the cliff
notes of everything we did

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and things you should be thinking about

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when we start moving from
the concrete into behavior.

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We start decoupling
our concrete solutions.

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Now, interfaces are very,
very powerful, right?

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I don't want pollution,

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but here's some really interesting things.

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Interfaces are gonna give
our program structure.

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They're gonna encourage
design by composition,

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and I showed you how
that composition works.

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And they also allow us to enable

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and enforce these clean
divisions between components,

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whether these, and a lot of times,

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these components are
gonna be these packages.

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We're gonna start talking about

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package on design eventually,

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and we're gonna really
talk about decoupling,

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and the interface can
really help with decoupling.

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Because remember, I
can define an interface

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that satisfies your concrete values.

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And you can define interfaces
that, my concrete values,

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and therefore, these interfaces which are

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isolated defined within
the packages themselves

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can create very clear divisions.

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And we have really nice
layers of decoupling

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through convention, not configuration.

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Now again, when we talk about decoupling,

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we're really trying to reduce dependency.

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We're trying to decouple components

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and packages as much as we can.

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And that's always going to lead

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to correctness, quality, and performance.

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It's going to allow code
base to grow over time

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and not suddenly come to a halt.

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And we've seen that already by

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some big projects in
the Go community, okay.

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Remember when it comes to grouping,

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we don't want to group by what we are.

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We want to group by what we do.

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We don't want to talk about who we are.

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That's configuration, right.

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Our parents made us who we are.

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But we, individually,
decide what we want to do.

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And that's how we want to group things.

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Or I want to be around people

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who are not necessarily like
myself from a DNA perspective,

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but who like to do the
same things that I do.

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We want to focus our code around

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that level of diversity, okay.

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Level of diversity.

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So that interface is going to help

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our code decouple from change.

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It's going allow our code
to maintain decoupling

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between packages or components.

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Or anyway, we got to really do our best

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to understand what is
going to change in our code

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and try to decouple that.

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And it really helps if you start

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with that concrete implementation.

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That same exercise we went to, okay.

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The same exercise.

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And if it's not clear what
an interface is doing for us,

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the benefit is not
clear, I want us to stop.

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I want us to learn more,

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and I want to question those things, okay.

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And the biggest thing here that we can do

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is really try to design
code and write APIs

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that defend against fraud and
not protect against accidents.

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To really focus on the idea

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that we want to design APIs
that are hard to misuse.

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I mean, JBD from Google

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said these two things
better than I ever could.

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"A good API is not just easy to use

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but also hard to misuse."

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And, "You can always embed but
you cannot always decompose

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big interfaces once they are out there."

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"Keep interfaces small."

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Compose interfaces as you need them.

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This is really going to help
you design better coding Go,

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not only today, but for tomorrow.