Kotlin lazy is nothing but the function which was taking a lambda and returns an instance of lazy, which can serve as implementing the property of lazy. The first call of getting is executing the lambda, which was passed through the lazy function, and we need to remember the result. The call of subsequent will return the remembered result.
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What is lazy and Lateinit in Kotlin?
lateinit can only be used with a var property whereas lazy will always be used with val property. A lateinit property can be reinitialised again and again as per the use whereas the lazy property can only be initialised once.
What is lazy evaluation in Kotlin?
The concept of lazy evaluation is all about evaluating expressions only if and when it becomes necessary at runtime. This is in contrast to eager evaluation, where every expression is eagerly evaluated even if the result or part of it is never used.
Is Kotlin by lazy thread-safe?
It is lazy and thread-safe, it initializes upon first call, much as Java's static initializers. You can declare an object at top level or inside a class or another object.
Which is thread-safe late init or lazy?
The Lazy initialization is thread-safe. Lateinit can only be used with var . Lazy initialization is used with the val property.
What is by lazy in Kotlin example?
Lazy is mainly used when you want to access some read-only property because the same object is accessed throughout.
What means Lateinit in Kotlin?
late initializationlateinit means late initialization. If you do not want to initialize a variable in the constructor instead you want to initialize it later on and if you can guarantee the initialization before using it, then declare that variable with lateinit keyword.
Is Kotlin lazy Singleton?
The Kotlin language provides some features called Object or in combination with a class Companion Object. These declarations are designed to implement the Singleton pattern in a native way. One thing to mention is that objects are constructed in a lazy way.
What's the difference between lazy and Lateinit?
Lazy initialization is one of the property Delegate-s, while late initialization requires the use of a language keyword. Lazy initialization applies only to val, and late initialization applies only to var fields. We can have a lazy field of a primitive type, but lateinit applies only to reference types.
What is a sealed class in Kotlin?
Sealed classes are used for representing restricted class hierarchies, when a value can have one of the types from a limited set, but cannot have any other type.
What is null safety Kotlin?
Kotlin null safety is a procedure to eliminate the risk of null reference from the code. Kotlin compiler throws NullPointerException immediately if it found any null argument is passed without executing any other statements. Kotlin's type system is aimed to eliminate NullPointerException form the code.
Why is lazy initialized?
Lazy initialization of an object means that its creation is deferred until it is first used. (For this topic, the terms lazy initialization and lazy instantiation are synonymous.) Lazy initialization is primarily used to improve performance, avoid wasteful computation, and reduce program memory requirements.
What is primary and secondary constructor in Kotlin?
The primary constructor initializes the class, while the secondary constructor is used to initialize the class and introduce some extra logic.
What is lazy initialization Kotlin?
Lazy Initialization lazy() is a function that takes a lambda and returns an instance of lazy which can serve as a delegate of lazy properties upon which it has been applied. It has been designed to prevent unnecessary initialization of objects. Lazy can be used only with non-NULLable variables.
What is a Kotlin sequence?
A sequence is a container Sequence
What does it mean to initialize a property in Kotlin?
Kotlin: Property must be initialized or be abstract. This basically means that we should either initialize the variable or mark it as abstract. On the other hand, there are some cases in which the variable can be assigned dynamically by for example dependency injection.
What is lateinit in Kotlin?
In Kotlin, every non-nullable class property that is declared in the class should be initialized either in the constructor or as part of the variable declaration. If we fail to do that, then the Kotlin compiler will complain about an error message: Kotlin: Property must be initialized or be abstract.
What is lazy initialization?
The concept of ‘lazy initialization’ was designed to prevent unnecessary initialization of objects. In Java, creating an object in a lazy and thread-safe way is not an easy thing to do. Patterns like Singleton have significant flaws in multithreading, testing, etc. – and they’re now widely known as anti-patterns to be avoided.
When we're accessing the lazyvalue for the first time, what happens?
When we’re accessing the lazyValue for the first time – an actual initialization happened, and the returned instance of the ClassWithHeavyInitialization class was assigned to the lazyValue reference. Subsequent access to the lazyValue returned the previously initialized object.
Is lazy initialization in Java?
We can see that using the lazy initialization pattern in Java is quite cumbersome. We need to write a lot of boilerplate code to achieve our goal. Luckily, the Kotlin language has built-in support for lazy initialization.
When to use lazy in Kotlin?
by lazy may be very useful when implementing read-only (val) properties that perform lazy-initialization in Kotlin.
What is lazy lambda?
A lambda passed to by lazy { ... } may capture references from the context where it is used into its closure .. It will then store the references and release them only once the property has been initialized. This may lead to object hierarchies, such as Android activities, not being released for too long (or ever, if the property remains accessible and is never accessed), so you should be careful about what you use inside the initializer lambda.
How to check if a lateinit property has been initialized?
If you hold a reference to an instance of Lazy , isInitialized () allows you to check whether it has already been initialized (and you can obtain such instance with reflection from a delegated property). To check whether a lateinit property has been initialized, you can use property::isInitialized since Kotlin 1.2.
What is lazy initialization?
lazy Initialization. by lazy may be very useful when implementing read-only properties that perform lazy-initialization in Kotlin. by lazy { ... } performs its initializer where the defined property is first used, not its declaration.
Where is lateinit initialized?
lateinit var can be initialized from anywhere the object is seen from , e.g. from inside a framework code, and multiple initialization scenarios are possible for different objects of a single class. by lazy { ... }, in turn, defines the only initializer for the property, which can be altered only by overriding the property in a subclass. If you want your property to be initialized from outside in a way probably unknown beforehand, use lateinit.
Is lazy var thread safe?
Initialization by lazy { ... } is thread-safe by default and guarantees that the initializer is invoked at most once (but this can be altered by using another lazy overload ). In case of lateinit var, it’s up to the user’s code to initialize the property correctly in multi-threaded environments.
Can lazy delegate be used for val properties?
lazy { ... } delegate can only be used for val properties, whereas lateinit can only be applied to var s, because it can’t be compiled to a final field, thus no immutability can be guaranteed;
