Package magnet

Enum Scoping

java.lang.Object

java.lang.Enum<Scoping>

magnet.Scoping

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<Scoping>

public enum Scoping
extends java.lang.Enum<Scoping>

Declares the way Magnet binds instances of @Instance-annotated classes into scopes. See each separate setting for more detail.

Enum Constant Summary

Enum Constants

Enum Constant	Description
DIRECT	Magnet will bind created instance into the same scope, in which this instance has been created.
TOPMOST	Magnet will bind created instance into the most top scope in the chain of scopes, where all dependencies for the created instance are still fulfilled.
UNSCOPED	Magnet will not bind created instance into any scope.

Method Summary

Modifier and Type	Method	Description
static Scoping	valueOf(java.lang.String name)	Returns the enum constant of this type with the specified name.
static Scoping[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

UNSCOPED

public static final Scoping UNSCOPED

Magnet will not bind created instance into any scope. This is equivalent to having a factory creating new instances each time when instance is requested.

In the example below, both instances typeA and typeB are not bound into the scope. Each new scope.getSingle(TypeB.class) call will return new instances of typeA and typeB.

 @Instance(type = TypeA.class, scoping = Scoping.UNSCOPED)
 class TypeA {
     TypeA() {}
 }

 @Instance(type = TypeB.class, scoping = Scoping.UNSCOPED)
 class TypeB {
     final TypeA typeA;
     TypeB(@NonNull TypeA dependency) {
         typeA = dependency;
     }
 }

 ...

 Scope scope = Magnet.createScope();

 TypeB typeB = scope.getSingle(TypeB.class);
 TypeA typeA = typeB.typeA;
 TypeA typeA2 = scope.getSingle(TypeA.class);
 typeA !== typeA2 // different instances

 

TOPMOST

public static final Scoping TOPMOST

Magnet will bind created instance into the most top scope in the chain of scopes, where all dependencies for the created instance are still fulfilled.

Scopes in Magnet can build a chain of parent-child relations (see Scope for more detail). This option allows binding instances of annotated class into a one of parent scopes. Magnet goes up the scope chain and checks, whether all dependencies for the instance can still be satisfied in that scope. The most top reached scope with satisfied dependencies is the scope, into which the instance gets bound.

In the example below both instances typeA and typeB are bound into root.

 @Instance(type = TypeA.class, scoping = Scoping.TOPMOST)
 class TypeA {
     TypeA() {}
 }

 @Instance(type = TypeB.class)
 class TypeB {
     final TypeA typeA;
     TypeB(@NonNull TypeA dependency) {
         typeA = dependency;
     }
 }

 ...

 Scope root = Magnet.createScope();
 Scope scope = root.createSubscope();

 TypeB typeB = scope.getSingle(TypeB.class);
 TypeA typeA = typeB.typeA;
 TypeA typeA2 = scope.getSingle(TypeA.class);
 typeA === typeA2 // same instance

 

Explanation:

• TypeA has no dependencies and thus it gets bound to root;
• TypeB depends on TypeA and because the instance of TypeA is available in root, and instance of TypeB can also be created in root.

In the example below we bind instance of typeA into scope and typeB instance gets bound into the scope too.

 @Instance(type = TypeA.class, scoping = Scoping.TOPMOST)
 class TypeA {
     TypeA() {}
 }

 @Instance(type = TypeB.class, scoping = Scoping.TOPMOST)
 class TypeB {
     final TypeA typeA;
     TypeB(@NonNull TypeA dependency) {
         typeA = dependency;
     }
 }

 ...

 Scope root = Magnet.createScope();
 Scope scope = root.createSubscope().bind(TypeA.class, new TypeA());

 TypeB typeB = scope.getSingle(TypeB.class);
 TypeA typeA = typeB.typeA;
 TypeA typeA2 = scope.getSingle(TypeA.class);
 typeA === typeA2 // same instance

 

Explanation:

• typeB cannot be bound in a scope above its dependencies;
• typeA is available in scope, thus the scope is the top most scope for dependent typeB too.

DIRECT

public static final Scoping DIRECT

Magnet will bind created instance into the same scope, in which this instance has been created.

In the example below, both instances typeA and typeB are bound into scope. Each new scope.getSingle(TypeB.class) call on the same instance of scope will return same instances of typeA and typeB.

 @Instance(type = TypeA.class, scoping = Scoping.DIRECT)
 class TypeA {
     TypeA() {}
 }

 @Instance(type = TypeB.class, scoping = Scoping.DIRECT)
 class TypeB {
     final TypeA typeA;
     TypeB(@NonNull TypeA dependency) {
         typeA = dependency;
     }
 }

 ...

 Scope root = Magnet.createScope();
 Scope scope = root.createSubscope();

 TypeB typeB = scope.getSingle(TypeB.class);
 TypeA typeA = typeB.typeA;
 TypeA typeA2 = scope.getSingle(TypeA.class);
 typeA === typeA2 // same instance

 

Method Detail

values

public static Scoping[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (Scoping c : Scoping.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static Scoping valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null