This post is part of Square’s “ Square Open Source ♥s Kotlin” series. For these cases, in Java and Kotlin alike, the use of Optional has its place.
As we’ve seen above, though, just having these annotations or a type system that can model nullability sometimes is not enough. Today’s Retrofit 2.3.0 release contains the same JSR 305 annotations for explicit nullability in Java and Kotlin as our recent Okio and OkHttp releases. interface MyApiService userSettings(): Observable**>
The second problem was noticed at testing time. With one of the Optional converters added alongside a serialization converter, requests whose bodies may deserialize to null can be changed to instead return an Optional. The first problem with this Optional is public constructor, which allows creating instances with arguments of not matching type. addCallAdapter(RxJava2CallAdapterFactory.create()) addConverterFactory(WireConverterFactory.create()) addConverterFactory(Java8OptionalConverterFactory.create()) Instead, they delegate to other converters for processing the bytes and then wrap the potentially-nullable result into an Optional. Unlike the other converters for libraries like Moshi, Gson, and Wire, these new ones are different in that they don’t actually convert bytes to objects. Retrofit 2.3.0 introduces two new delegating converters for the Optional types in Guava and Java 8. Thus, in order to represent the absence of a value for the response body inside this stream we need an abstraction like Optional. If we’re using RxJava 2 and the converter for Settings returns null an exception will occur.
RxJava 2 differs from RxJava 1 in that it does not allow null in its streams. interface MyApiService userSettings(): Observable Just because you can explicitly express nullability, however, does not mean that null is always allowed.įor example, Retrofit provides adapters for RxJava 1.x and 2.x which allow modeling your requests as a single-element stream. (keys always converted to strings) Optional attributes - as nullable fields. * 2.0.1 */ static boolean isNullable(MethodParameter parameter) represents a nullable Kotlin type or an * optional parameter (with a default value in the Kotlin declaration).With nullability being a first-class citizen in Kotlin’s type system, the need for an Optional type seems all but diminished. * * true} if MethodParameter} is nullable. Its declaring method can reference a * Kotlin function, property or interface property. ** * Returns whether the given MethodParameter} is nullable. Properly handles null value ('Not set' state is different from 'Null set') Is mutable Uses Kotlin built-in null-safety, type parameter can be either nullable or non-nullable which affects all methods.
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