Scala why not

A different form of qualification is private[this]. In addition, the restrictions for unqualified private apply. Members marked private without a qualifier are called class-private , whereas members labeled with private[this] are called object-private.

Class-private or object-private members may not be abstract, and may not have protected or override modifiers. They are not inherited by subclasses and they may not override definitions in parent classes. The protected modifier applies to class member definitions. Protected members of a class can be accessed from within.

A different form of qualification is protected[this]. In addition, the restrictions for unqualified protected apply. The override modifier applies to class member definitions or declarations. It is mandatory for member definitions or declarations that override some other concrete member definition in a parent class. If an override modifier is given, there must be at least one overridden member definition or declaration either concrete or abstract.

The override modifier has an additional significance when combined with the abstract modifier. That modifier combination is only allowed for value members of traits. Note that the abstract override modifier combination does not influence the concept whether a member is concrete or abstract.

A member is abstract if only a declaration is given for it; it is concrete if a full definition is given. The abstract modifier is used in class definitions. It is redundant for traits, and mandatory for all other classes which have incomplete members.

Only abstract classes and traits can have abstract term members. The abstract modifier can also be used in conjunction with override for class member definitions.

In that case the previous discussion applies. The final modifier applies to class member definitions and to class definitions. A final class member definition may not be overridden in subclasses. A final class may not be inherited by a template. Members of final classes or objects are implicitly also final, so the final modifier is generally redundant for them, too. Note, however, that constant value definitions do require an explicit final modifier, even if they are defined in a final class or object.

The sealed modifier applies to class definitions. A sealed class may not be directly inherited, except if the inheriting template is defined in the same source file as the inherited class. However, subclasses of a sealed class can be inherited anywhere. The lazy modifier applies to value definitions. A lazy value is initialized the first time it is accessed which might never happen at all.

Attempting to access a lazy value during its initialization might lead to looping behavior. If an exception is thrown during initialization, the value is considered uninitialized, and a later access will retry to evaluate its right hand side. Here, accesses to the method f can appear anywhere within Outer , but not outside it.

Accesses to method g can appear anywhere within the package outerpkg. Finally, accesses to method h can appear anywhere within package outerpkg , including packages contained in it. A useful idiom to prevent clients of a class from constructing new instances of that class is to declare the class abstract and sealed :. For instance, in the code above clients can create instances of class m.

C only by calling the nextC method of an existing m. C object; it is not possible for clients to create objects of class m. C directly. Indeed the following two lines are both in error:.

A similar access restriction can be achieved by marking the primary constructor private example. It is illegal to define two formal value parameters with the same name.

If no formal parameter sections are given, an empty parameter section is assumed. The formal parameter declaration may contain modifiers, which then carry over to the accessor definition s. When access modifiers are given for a parameter, but no val or var keyword, val is assumed. A formal parameter prefixed by val or var may not at the same time be a call-by-name parameter.

AnyRef is assumed. The following example illustrates val and var parameters of a class C :. A class may have additional constructors besides the primary constructor. The self constructor invocation must construct a generic instance of the class. The signature and the self constructor invocation of a constructor definition are type-checked and evaluated in the scope which is in effect at the point of the enclosing class definition, augmented by any type parameters of the enclosing class and by any early definitions of the enclosing template.

The rest of the constructor expression is type-checked and evaluated as a function body in the current class. However, unlike other methods, constructors are never inherited. To prevent infinite cycles of constructor invocations, there is the restriction that every self constructor invocation must refer to a constructor definition which precedes it i.

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Asked 5 years ago. Active 8 months ago. Viewed 24k times. If I want to do something like: if! Does it looks like? Shaido 24k 20 20 gold badges 61 61 silver badges 68 68 bronze badges.

Jeff Hu Jeff Hu 1 1 gold badge 5 5 silver badges 20 20 bronze badges. I apologize for not being clear. I am asking if! The condition can be anything. Example: Scala. Previous Inheritance in Scala. Next Scala Singleton and Companion Objects. Recommended Articles. Scala SortedMap addString method with a start, a separator and an end with example. Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? Please use ide. Load Comments.

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