74 lines
1.8 KiB
Plaintext
74 lines
1.8 KiB
Plaintext
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== Why is this an issue?
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Functional interfaces can be instantiated from lambda expressions directly.
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If the only purpose of a class or a singleton object is to implement a functional interface,
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that class or object is redundant and should be replaced with a lambda expression.
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=== What is the potential impact?
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==== Complexity
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When an interface is declared _functional_, SAM conversion is enabled for that interface.
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This means that any lambda expression that matches the interface's single function's signature
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can be converted into an instance of the interface
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without the need for an
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explicit class or singleton object to implement the interface.
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This change makes the code more concise and easier to read.
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== How to fix it
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Replace the class or singleton object with a lambda expression that implements the interface's single function.
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=== Code examples
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==== Noncompliant code example
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[source,kotlin]
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----
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fun interface ProgressCallback {
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fun progressChanged(percent: Double)
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}
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fun loadResource(callback: ProgressCallback) {
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// ...
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}
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----
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[source,kotlin,diff-id=1,diff-type=noncompliant]
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----
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val resource = loadResource(object: ProgressCallback { // Noncompliant
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override fun progressChanged(percent: Double) {
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// ...
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}
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})
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val callback = object: ProgressCallback {
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override fun progressChanged(percent: Double) { // Noncompliant
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// ...
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}
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}
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----
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==== Compliant solution
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[source,kotlin,diff-id=1,diff-type=compliant]
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----
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val resource = loadResource() { // Compliant
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// ...
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}
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val callback = ProgressCallback { // Compliant
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// ...
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}
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----
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== Resources
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=== Documentation
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* https://kotlinlang.org/docs/fun-interfaces.html[Kotlin Docs, Functional (SAM) interfaces]
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=== Articles & blog posts
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* https://www.baeldung.com/kotlin/sam-conversions[Baeldung, SAM Conversions in Kotlin]
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