Scala option code#
This is very unsafe code since we are at risk of NullReferenceException. Public string City // can be nullĬonsole.WriteLine(.ToUpper()) Let’s assume that Article does not have to have an Author, the Author does not have to have an Address and the address does not have to have a City (for example this data can be missing from our database).
Imagine we have a nested data model and want to call some method on a property nested deeply inside an object graph. We will see how it can help us understand monads in Scala! Null-conditional operator
Note: might return different results for different runs, unless the underlying collection type is ordered.Įxample: List(1, 2, 3, 4).Today I will talk about an awesome feature of C# 6.0. Note: will not terminate for infinite-sized collections. The head of the collection is the last cumulative result. By passing the toInt method into the map method, you can convert every element in the collection into a Some or None value: scala> bag. Produces a collection containing cumulative results of applying the operator going right to left. This is the documentation for the Scala standard library. Definition Classes TraversableLike → TraversableOnce → GenTraversableOnce def hashCode () : Int Simply stated, instead of returning one object when a function succeeds and null when it fails, your function should instead return an instance of an Option, where the instance is either. Im trying to achieve with Option s what can be done with Seq uences, where you turn a. Implicit This member is added by an implicit conversion from Option to Iterable performed by method option2Iterable in scala.Option. A powerful Scala idiom is to use the Option class when returning a value from a function that can be null. Scala Transform FutureOptionX into OptionFutureX. True if this collection is known to have finite size, false otherwise. However, checking hasDefiniteSize can provide an assurance that size is well-defined and non-termination is not a concern. These methods always attempt a traversal without checking first that hasDefiniteSize returns true.
The typical failure mode is an infinite loop. Note: many collection methods will not work on collections of infinite sizes. Non-empty Iterators usually return false even if they were created from a collection with a known finite size. It returns false if the stream is not yet evaluated to the end. For a non-strict collection such as Stream, the predicate returns true if all elements have been computed. All strict collections are known to have finite size. Tests whether this iterable collection is known to have a finite size. Definition Classes TraversableOnce → GenTraversableOnce final def asInstanceOf : T0 Nil for list concatenation or 0 for summation) and may be evaluated more than once seqopĪn operator used to accumulate results within a partition combopĪn associative operator used to combine results from different partitions Implicit This member is added by an implicit conversion from Option to Iterable performed by method option2Iterable in scala.Option. The initial value for the accumulated result of the partition - this will typically be the neutral element for the seqop operator (e.g. The most idiomatic way to use an scala.Option instance is to treat it as a collection or monad and use map, flatMap, filter, or foreach: val name: Option = request getParameter "name" Instances of Option are either an instance of scala.Some or the object None.
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