Peanuts

If you use Kotlin flows to manage your Jetpack Compose UI states, chances are that this code is familiar to you on a daily basis.

You have a state:

data class MyScreenState(
    val isLoading: Boolean = false,
    // ...
)

And, in your ViewModel, you init and expose that state:

class MyScreenViewModel : ViewModel() {
    private val _state = MutableStateFlow(MyScreenState())
    val state = _state.asStateFlow()
}

Then, whenever you want to update the screen state, you need to do something like:

_state.update { currentState -> currentState.copy(isLoading = true) }

---

Why • Installation • Usage

---

Why Peanuts?

Even tho the code above is simple, it has 2 main flaws:

1. You always need to remember to copy the current state to create a new state;
2. Due to that, you need to write the same code over and over again.

Peanuts is a very simple library that uses KSP and KotlinPoet to simplify the screen state updates. It will automatically generate an extension function for you, like this one:

fun MutableStateFlow<MyScreenState>.update(isLoading: Boolean = value.isLoading, ...) =
    update { it.copy(isLoading = isLoading, ...) }

Allowing you to update your screen state simply with:

_state.update(isLoading = true)

Installation

1. Add KSP plugin:

In your project build gradle:

plugins {
    //...
    id 'com.google.devtools.ksp' version '1.7.20-1.0.7' // Depends on your kotlin version
}

In your app build gradle:

plugins {
    // ...
    id 'com.google.devtools.ksp'
}

2. Add dependency:

dependencies {
    implementation 'dev.pinkroom:peanuts:<latest_version>'
    ksp 'dev.pinkroom:peanuts:<latest_version>'
}

3. Add KSP generated folders as source directories:

android {
    // ...
    applicationVariants.all { variant ->
        kotlin.sourceSets {
            getByName(variant.name) {
                kotlin.srcDir("build/generated/ksp/${variant.name}/kotlin")
            }
        }
    }
}

Note: This is only needed due to this issue.

Usage

First, you need to annotate your screen states with @PeanutState:

@PeanutState
data class MyScreenState(
    val isLoading: Boolean = false,
    // ...
)

After your code compiles, updating your screen state is peanuts:

_state.update(isLoading = true)

License

Copyright 2022 Pink Room, Lda

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.