Kotlin Delegates Check

Aleksei Jegorov
Jul 6, 2020 · 1 min read

Kotlin languages likes to work with lazy property initialization.

Methods that will be implemented in proper time.

Usual usage is something like this:

lateinit var loginButton: LoginButton

or like this: Defer the cost of initialization until they’re actually needed.

val tvOutput by lazy { findViewById<TextView>(R.id.textViewOutput) }

But we can also use a built-in delegate.

Delegate object is a reference type variable that use holds reference to a method.

Delegate Vetoable

Functional interface of lambda passed to the vetoable is called before the assignment of a new value to property. Returning false from the lambda allows you to “veto” the assignment, so we apply sanctions and default value will be returned. Otherwise, True means the positive scenario.

So, it very simple to use anyway

Delegate Observable

Each time value changes it calls the delegate to perform some action and assign a new value.

Conclusion

It is nice mechanism to set new value or make check in functional “Lambda” way.

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Aleksei Jegorov

Written by

Java, Kotlin, T-SQL, ASP.NET Core C#, Angular2, ReactJs, Android Java native developer in Estonia, Tallinn. https://github.com/wider2?tab=repositories

The Startup

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Aleksei Jegorov

Written by

Java, Kotlin, T-SQL, ASP.NET Core C#, Angular2, ReactJs, Android Java native developer in Estonia, Tallinn. https://github.com/wider2?tab=repositories

The Startup

Get smarter at building your thing. Follow to join The Startup’s +8 million monthly readers & +786K followers.

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