Fixed
Status Update
Comments
mm...@commonsware.com <mm...@commonsware.com> #2
Partly, this is my fault -- val is not that useful in the @Model context, since @Model relies on mutability. I am used to thinking in terms of immutable viewstates and screwed this up.
However, it probably should not crash this way. Either it should work (with a never-changing value) or it should fail with a "are you *really* sure you want this here?" sort of error.
However, it probably should not crash this way. Either it should work (with a never-changing value) or it should fail with a "are you *really* sure you want this here?" sort of error.
lu...@gmail.com <lu...@gmail.com> #3
I'd like to add that declaring `canProceed` as a `var` won't crash the app.
The extension function is avoidable by just having the `get()`-getter function inside the class itself. That also avoids the crash.
The extension function is avoidable by just having the `get()`-getter function inside the class itself. That also avoids the crash.
ch...@google.com <ch...@google.com> #4
Try,
@Model
data class AgreementViewState(var terms: Boolean, var privacy: Boolean) {
val canProceed get() = terms && privacy
}
(note the addtion of get()) which seems to be what you intended. `val canProceed = terms && privacy` is not a derived property, rather, it is an initialized property.
@Model
data class AgreementViewState(var terms: Boolean, var privacy: Boolean) {
val canProceed get() = terms && privacy
}
(note the addtion of get()) which seems to be what you intended. `val canProceed = terms && privacy` is not a derived property, rather, it is an initialized property.
mm...@commonsware.com <mm...@commonsware.com> #5
Yes, that echoes comment #3 . It too works, akin to fun canProceed(), an external extension function, and a var. So, in terms of having working approaches, I'm good.
I'll still argue that the initialized val shouldn't blow up the way that it does, though.
I'll still argue that the initialized val shouldn't blow up the way that it does, though.
[Deleted User] <[Deleted User]> #6
Does Model support val properties in the primary constructor? What if I want to update (rebind) view with the NEW data from the API for e.g. and not necessarily update var fields in the existing @Model data, is that supported?
It is generally advised in the Kotlin community to "limit mutability" and use 'val' as much as possible (book Effective Kotlin by Marcin Moskala), while here you advise all @Model data to use var fields?
Epoxy library works great with immutable models, and always properly rebinds existing views based on new immutable Model objects you pass into it.
It is generally advised in the Kotlin community to "limit mutability" and use 'val' as much as possible (book Effective Kotlin by Marcin Moskala), while here you advise all @Model data to use var fields?
Epoxy library works great with immutable models, and always properly rebinds existing views based on new immutable Model objects you pass into it.
cl...@google.com <cl...@google.com>
ap...@google.com <ap...@google.com> #7
Project: platform/frameworks/support
Branch: androidx-master-dev
commit fcf76b3241844f18106d6e850004952046d4bfb6
Author: Leland Richardson <lelandr@google.com>
Date: Wed May 13 16:58:59 2020
Deprecate @Model
Relnote: “
@Model annotation is now deprecated. Use state and mutableStateOf as alternatives. This deprecation decision was reached after much careful discussion.
Justification
=============
Rationale includes but is not limited to:
- Reduces API surface area and concepts we need to teach
- More closely aligns with other comparable toolkits (Swift UI, React, Flutter)
- Reversible decision. We can always bring @Model back later.
- Removes corner-case usage and difficult to answer questions about configuring @Model as things we need to handle
- @Model data classes, equals, hashcode, etc.
- How do I have some properties “observed” and others not?
- How do I specify structural vs. referential equality to be used in observation?
- Reduces “magic” in the system. Would reduce the likelihood of someone assuming system was smarter than it is (ie, it knowing how to diff a list)
- Makes the granularity of observation more intuitive.
- Improves refactorability from variable -> property on class
- Potentially opens up possibilities to do hand-crafted State-specific optimizations
- More closely aligns with the rest of the ecosystem and reduces ambiguity towards immutable or us “embracing mutable state”
Migration Notes
===============
Almost all existing usages of @Model are fairly trivially transformed in one of two ways. The example below has a @Model class with two properties just for the sake of example, and has it being used in a composable.
```
@Model class Position(
var x: Int,
var y: Int
)
@Composable fun Example() {
var p = remember { Position(0, 0) }
PositionChanger(
position=p,
onXChange={ p.x = it }
onYChange={ p.y = it }
)
}
```
Alternative 1: Use State<OriginalClass> and create copies.
----------------------------------------------------------
This approach is made easier with Kotlin’s data classes. Essentially, make all previously `var` properties into `val` properties of a data class, and then use `state` instead of `remember`, and assign the state value to cloned copies of the original using the data class `copy(...)` convenience method.
It’s important to note that this approach only works when the only mutations to that class were done in the same scope that the `State` instance is created. If the class is internally mutating itself outside of the scope of usage, and you are relying on the observation of that, then the next approach is the one you will want to use.
```
data class Position(
val x: Int,
val y: Int
)
@Composable fun Example() {
var p by state { Position(0, 0) }
PositionChanger(
position=p,
onXChange={ p = p.copy(x=it) }
onYChange={ p = p.copy(y=it) }
)
}
```
Alternative 2: Use mutableStateOf and property delegates
--------------------------------------------------------
This approach is made easier with Kotlin’s property delegates and the `mutableStateOf` API which allows you to create MutableState instances outside of composition. Essentially, replace all `var` properties of the original class with `var` properties with `mutableStateOf` as their property delegate. This has the advantage that the usage of the class will not change at all, only the internal implementation of it. The behavior is not completely identical to the original example though, as each property is now observed/subscribed to individually, so the recompositions you see after this refactor could be more narrow (a good thing).
```
class Position(x: Int, y: Int) {
var x by mutableStateOf(x)
var y by mutableStateOf(y)
}
// source of Example is identical to original
@Composable fun Example() {
var p = remember { Position(0, 0) }
PositionChanger(
position=p,
onXChange={ p.x = it }
onYChange={ p.y = it }
)
}
```
“
Bug: 156546430
Bug: 152993135
Bug: 152050010
Bug: 148866188
Bug: 148422703
Bug: 148394427
Bug: 146362815
Bug: 146342522
Bug: 143413369
Bug: 135715219
Bug: 126418732
Bug: 147088098
Bug: 143263925
Bug: 139653744
Change-Id: I409e8c158841eae1dd548b33f1ec80bb609cba31
M compose/compose-compiler-hosted/integration-tests/src/test/java/androidx/compose/plugins/kotlin/frames/FrameDiagnosticTests.kt
M compose/compose-runtime/api/0.1.0-dev12.txt
M compose/compose-runtime/api/current.txt
M compose/compose-runtime/api/public_plus_experimental_0.1.0-dev12.txt
M compose/compose-runtime/api/public_plus_experimental_current.txt
M compose/compose-runtime/api/restricted_0.1.0-dev12.txt
M compose/compose-runtime/api/restricted_current.txt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/ComposeBenchmark.kt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/SiblingBenchmark.kt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/dbmonster/DbMonster.kt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/realworld4/RealWorld4_DataModels.kt
M compose/compose-runtime/samples/src/main/java/androidx/compose/samples/ModelSamples.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/FrameManager.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/Model.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/MutableState.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/Observe.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/Recompose.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/StableMarker.kt
M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/ModelObserverBenchmark.kt
M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/RadioGroupBenchmark.kt
M ui/integration-tests/demos/src/main/java/androidx/ui/demos/DemoColorPalette.kt
M ui/integration-tests/src/main/java/androidx/ui/integration/test/foundation/RectsInColumnSharedModelTestCase.kt
M ui/ui-android-view/integration-tests/android-view-demos/src/main/java/androidx/ui/androidview/demos/WebComponentActivity.kt
M ui/ui-animation/src/main/java/androidx/ui/animation/AnimatedValueEffects.kt
M ui/ui-animation/src/main/java/androidx/ui/animation/Transition.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/AndroidLayoutDrawTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/AndroidViewCompatTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/ClipTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/DrawShadowTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/ModelReadsTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/OpacityTest.kt
D ui/ui-core/src/androidTest/java/androidx/ui/core/test/ValueModel.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/WithConstraintsTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/res/ResourcesTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/semantics/SemanticsTests.kt
M ui/ui-core/src/main/java/androidx/ui/core/ModelObserver.kt
M ui/ui-core/src/main/java/androidx/ui/res/Resources.kt
M ui/ui-core/src/test/java/androidx/ui/core/selection/SelectionManagerDragTest.kt
M ui/ui-core/src/test/java/androidx/ui/core/selection/SelectionManagerLongPressDragTest.kt
M ui/ui-core/src/test/java/androidx/ui/core/selection/SelectionManagerTest.kt
M ui/ui-foundation/src/androidTest/java/androidx/ui/foundation/DeterminateProgressTest.kt
M ui/ui-layout/src/androidTest/java/androidx/ui/layout/test/ContainerTest.kt
M ui/ui-layout/src/androidTest/java/androidx/ui/layout/test/OnPositionedTest.kt
M ui/ui-material/api/0.1.0-dev12.txt
M ui/ui-material/api/current.txt
M ui/ui-material/api/public_plus_experimental_0.1.0-dev12.txt
M ui/ui-material/api/public_plus_experimental_current.txt
M ui/ui-material/api/restricted_0.1.0-dev12.txt
M ui/ui-material/api/restricted_current.txt
M ui/ui-material/integration-tests/material-demos/src/main/java/androidx/ui/material/demos/DynamicThemeActivity.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/DrawerTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ProgressIndicatorTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/RadioGroupUiTest.kt
M ui/ui-material/src/main/java/androidx/ui/material/Color.kt
M ui/ui-material/src/main/java/androidx/ui/material/Scaffold.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/AndroidComposeTestCaseRunnerTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/MultipleComposeRootsTest.kt
M ui/ui-text/src/main/java/androidx/ui/text/CoreText.kt
M ui/ui-text/src/main/java/androidx/ui/text/CoreTextField.kt
https://android-review.googlesource.com/1311293
Branch: androidx-master-dev
commit fcf76b3241844f18106d6e850004952046d4bfb6
Author: Leland Richardson <lelandr@google.com>
Date: Wed May 13 16:58:59 2020
Deprecate @Model
Relnote: “
@Model annotation is now deprecated. Use state and mutableStateOf as alternatives. This deprecation decision was reached after much careful discussion.
Justification
=============
Rationale includes but is not limited to:
- Reduces API surface area and concepts we need to teach
- More closely aligns with other comparable toolkits (Swift UI, React, Flutter)
- Reversible decision. We can always bring @Model back later.
- Removes corner-case usage and difficult to answer questions about configuring @Model as things we need to handle
- @Model data classes, equals, hashcode, etc.
- How do I have some properties “observed” and others not?
- How do I specify structural vs. referential equality to be used in observation?
- Reduces “magic” in the system. Would reduce the likelihood of someone assuming system was smarter than it is (ie, it knowing how to diff a list)
- Makes the granularity of observation more intuitive.
- Improves refactorability from variable -> property on class
- Potentially opens up possibilities to do hand-crafted State-specific optimizations
- More closely aligns with the rest of the ecosystem and reduces ambiguity towards immutable or us “embracing mutable state”
Migration Notes
===============
Almost all existing usages of @Model are fairly trivially transformed in one of two ways. The example below has a @Model class with two properties just for the sake of example, and has it being used in a composable.
```
@Model class Position(
var x: Int,
var y: Int
)
@Composable fun Example() {
var p = remember { Position(0, 0) }
PositionChanger(
position=p,
onXChange={ p.x = it }
onYChange={ p.y = it }
)
}
```
Alternative 1: Use State<OriginalClass> and create copies.
----------------------------------------------------------
This approach is made easier with Kotlin’s data classes. Essentially, make all previously `var` properties into `val` properties of a data class, and then use `state` instead of `remember`, and assign the state value to cloned copies of the original using the data class `copy(...)` convenience method.
It’s important to note that this approach only works when the only mutations to that class were done in the same scope that the `State` instance is created. If the class is internally mutating itself outside of the scope of usage, and you are relying on the observation of that, then the next approach is the one you will want to use.
```
data class Position(
val x: Int,
val y: Int
)
@Composable fun Example() {
var p by state { Position(0, 0) }
PositionChanger(
position=p,
onXChange={ p = p.copy(x=it) }
onYChange={ p = p.copy(y=it) }
)
}
```
Alternative 2: Use mutableStateOf and property delegates
--------------------------------------------------------
This approach is made easier with Kotlin’s property delegates and the `mutableStateOf` API which allows you to create MutableState instances outside of composition. Essentially, replace all `var` properties of the original class with `var` properties with `mutableStateOf` as their property delegate. This has the advantage that the usage of the class will not change at all, only the internal implementation of it. The behavior is not completely identical to the original example though, as each property is now observed/subscribed to individually, so the recompositions you see after this refactor could be more narrow (a good thing).
```
class Position(x: Int, y: Int) {
var x by mutableStateOf(x)
var y by mutableStateOf(y)
}
// source of Example is identical to original
@Composable fun Example() {
var p = remember { Position(0, 0) }
PositionChanger(
position=p,
onXChange={ p.x = it }
onYChange={ p.y = it }
)
}
```
“
Bug: 156546430
Bug: 152993135
Bug: 152050010
Bug: 148866188
Bug: 148422703
Bug: 148394427
Bug: 146362815
Bug: 146342522
Bug: 143413369
Bug: 135715219
Bug: 126418732
Bug: 147088098
Bug: 143263925
Bug: 139653744
Change-Id: I409e8c158841eae1dd548b33f1ec80bb609cba31
M compose/compose-compiler-hosted/integration-tests/src/test/java/androidx/compose/plugins/kotlin/frames/FrameDiagnosticTests.kt
M compose/compose-runtime/api/0.1.0-dev12.txt
M compose/compose-runtime/api/current.txt
M compose/compose-runtime/api/public_plus_experimental_0.1.0-dev12.txt
M compose/compose-runtime/api/public_plus_experimental_current.txt
M compose/compose-runtime/api/restricted_0.1.0-dev12.txt
M compose/compose-runtime/api/restricted_current.txt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/ComposeBenchmark.kt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/SiblingBenchmark.kt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/dbmonster/DbMonster.kt
M compose/compose-runtime/compose-runtime-benchmark/src/androidTest/java/androidx/compose/benchmark/realworld4/RealWorld4_DataModels.kt
M compose/compose-runtime/samples/src/main/java/androidx/compose/samples/ModelSamples.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/FrameManager.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/Model.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/MutableState.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/Observe.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/Recompose.kt
M compose/compose-runtime/src/commonMain/kotlin/androidx/compose/StableMarker.kt
M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/ModelObserverBenchmark.kt
M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/RadioGroupBenchmark.kt
M ui/integration-tests/demos/src/main/java/androidx/ui/demos/DemoColorPalette.kt
M ui/integration-tests/src/main/java/androidx/ui/integration/test/foundation/RectsInColumnSharedModelTestCase.kt
M ui/ui-android-view/integration-tests/android-view-demos/src/main/java/androidx/ui/androidview/demos/WebComponentActivity.kt
M ui/ui-animation/src/main/java/androidx/ui/animation/AnimatedValueEffects.kt
M ui/ui-animation/src/main/java/androidx/ui/animation/Transition.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/AndroidLayoutDrawTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/AndroidViewCompatTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/ClipTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/DrawShadowTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/ModelReadsTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/OpacityTest.kt
D ui/ui-core/src/androidTest/java/androidx/ui/core/test/ValueModel.kt
M ui/ui-core/src/androidTest/java/androidx/ui/core/test/WithConstraintsTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/res/ResourcesTest.kt
M ui/ui-core/src/androidTest/java/androidx/ui/semantics/SemanticsTests.kt
M ui/ui-core/src/main/java/androidx/ui/core/ModelObserver.kt
M ui/ui-core/src/main/java/androidx/ui/res/Resources.kt
M ui/ui-core/src/test/java/androidx/ui/core/selection/SelectionManagerDragTest.kt
M ui/ui-core/src/test/java/androidx/ui/core/selection/SelectionManagerLongPressDragTest.kt
M ui/ui-core/src/test/java/androidx/ui/core/selection/SelectionManagerTest.kt
M ui/ui-foundation/src/androidTest/java/androidx/ui/foundation/DeterminateProgressTest.kt
M ui/ui-layout/src/androidTest/java/androidx/ui/layout/test/ContainerTest.kt
M ui/ui-layout/src/androidTest/java/androidx/ui/layout/test/OnPositionedTest.kt
M ui/ui-material/api/0.1.0-dev12.txt
M ui/ui-material/api/current.txt
M ui/ui-material/api/public_plus_experimental_0.1.0-dev12.txt
M ui/ui-material/api/public_plus_experimental_current.txt
M ui/ui-material/api/restricted_0.1.0-dev12.txt
M ui/ui-material/api/restricted_current.txt
M ui/ui-material/integration-tests/material-demos/src/main/java/androidx/ui/material/demos/DynamicThemeActivity.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/DrawerTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ProgressIndicatorTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/RadioGroupUiTest.kt
M ui/ui-material/src/main/java/androidx/ui/material/Color.kt
M ui/ui-material/src/main/java/androidx/ui/material/Scaffold.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/AndroidComposeTestCaseRunnerTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/MultipleComposeRootsTest.kt
M ui/ui-text/src/main/java/androidx/ui/text/CoreText.kt
M ui/ui-text/src/main/java/androidx/ui/text/CoreTextField.kt
Description
Android Studio 3.5 Beta 1
Build #AI-191.6707.61.35.5677133, built on June 20, 2019
JRE: 1.8.0_202-release-1483-b39-5396753 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Linux 5.0.0-25-generic
(specifically the one from the Compose repo)
Version of Gradle Plugin: 3.5.0-beta05
Version of Gradle: whatever frameworks/support/ui is using -- your setup is too damn complicated...
Version of Kotlin: 1.3.41
OS: Ubuntu 19.04
Steps to Reproduce:
Step #1: Define a @Model as a top-level class:
@Model
data class AgreementViewState(var terms: Boolean, var privacy: Boolean) {
val canProceed = terms && privacy
}
Step #2: Attempt to use that @Model in a @Composable:
@Composable
private fun Agreement() {
Padding(8.dp) {
val viewState = +model { AgreementViewState(true, false) }
Column(mainAxisAlignment = MainAxisAlignment.Start, crossAxisAlignment = CrossAxisAlignment.Start) {
Row(mainAxisAlignment = MainAxisAlignment.Start) {
Checkbox(
checked = viewState.terms,
onCheckedChange = { viewState.terms = it }
)
Text(text = "I agree to the terms and conditions")
}
Row(mainAxisAlignment = MainAxisAlignment.Start) {
Checkbox(
checked = viewState.privacy,
onCheckedChange = { viewState.privacy = it }
)
Text(text = "I agree to the privacy policy")
}
Text(text = if (viewState.canProceed) "You may proceed" else "Please indicate your agreement")
}
}
}
Expected Results: No crashes
Actual Results: A crash from generated code when the @Composable is called:
java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter r
at androidx.compose.frames.FramesKt._readable(Unknown Source:2)
at androidx.ui.foundation.demos.AgreementViewState.getTerms(Unknown Source:5)
at androidx.ui.foundation.demos.AgreementViewState.<init>(MainActivity.kt:230)
Note that this works:
@Model
data class AgreementViewState(var terms: Boolean, var privacy: Boolean) {
fun canProceed() = terms && privacy
}
...and this works:
@Model
data class AgreementViewState(var terms: Boolean, var privacy: Boolean) {
// fun canProceed() = terms && privacy
}
val AgreementViewState.canProceed
get() = terms && privacy
But, IMHO, the original form ought to work as well, as it seems to be the most natural form of a derived property in Kotlin.
Thanks for considering this!