[Merged by Bors] - Add set_if_neq method to DetectChanges trait (Rebased)
#6853
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alice-i-cecile
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alice-i-cecile
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Dec 5, 2022
Something about how GitHub does sequential non-linear merges, I think. It was an unusually tangled rebase for sure. |
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Is it |
Dessix
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set_if_differs method to DetectChanges trait (Rebased)set_if_neq method to DetectChanges trait (Rebased)
@mockersf I had quoted the original PR name prior to updating it. I've altered this one to match the content. |
hymm
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Dec 11, 2022
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Dec 11, 2022
# Objective
Change detection can be spuriously triggered by setting a field to the same value as before. As a result, a common pattern is to write:
```rust
if *foo != value {
*foo = value;
}
```
This is confusing to read, and heavy on boilerplate.
Adopted from #5373, but untangled and rebased to current `bevy/main`.
## Solution
1. Add a method to the `DetectChanges` trait that implements this boilerplate when the appropriate trait bounds are met.
2. Document this minor footgun, and point users to it.
## Changelog
* added the `set_if_neq` method to avoid triggering change detection when the new and previous values are equal. This will work on both components and resources.
## Migration Guide
If you are manually checking if a component or resource's value is equal to its new value before setting it to avoid triggering change detection, migrate to the clearer and more convenient `set_if_neq` method.
## Context
Related to #2363 as it avoids triggering change detection, but not a complete solution (as it still requires triggering it when real changes are made).
Co-authored-by: Zoey <Dessix@Dessix.net>
bors
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set_if_neq method to DetectChanges trait (Rebased)set_if_neq method to DetectChanges trait (Rebased)
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Jan 6, 2023
# Objective - The doctest for `Mut::map_unchanged` uses a fake function `set_if_not_equal` to demonstrate usage. - Now that #6853 has been merged, we can use `Mut::set_if_neq` directly instead of mocking it.
james7132
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Jan 21, 2023
# Objective - The doctest for `Mut::map_unchanged` uses a fake function `set_if_not_equal` to demonstrate usage. - Now that bevyengine#6853 has been merged, we can use `Mut::set_if_neq` directly instead of mocking it.
alradish
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Jan 22, 2023
…e#6853) # Objective Change detection can be spuriously triggered by setting a field to the same value as before. As a result, a common pattern is to write: ```rust if *foo != value { *foo = value; } ``` This is confusing to read, and heavy on boilerplate. Adopted from bevyengine#5373, but untangled and rebased to current `bevy/main`. ## Solution 1. Add a method to the `DetectChanges` trait that implements this boilerplate when the appropriate trait bounds are met. 2. Document this minor footgun, and point users to it. ## Changelog * added the `set_if_neq` method to avoid triggering change detection when the new and previous values are equal. This will work on both components and resources. ## Migration Guide If you are manually checking if a component or resource's value is equal to its new value before setting it to avoid triggering change detection, migrate to the clearer and more convenient `set_if_neq` method. ## Context Related to bevyengine#2363 as it avoids triggering change detection, but not a complete solution (as it still requires triggering it when real changes are made). Co-authored-by: Zoey <Dessix@Dessix.net>
alradish
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Jan 22, 2023
# Objective - The doctest for `Mut::map_unchanged` uses a fake function `set_if_not_equal` to demonstrate usage. - Now that bevyengine#6853 has been merged, we can use `Mut::set_if_neq` directly instead of mocking it.
ItsDoot
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Feb 1, 2023
…e#6853) # Objective Change detection can be spuriously triggered by setting a field to the same value as before. As a result, a common pattern is to write: ```rust if *foo != value { *foo = value; } ``` This is confusing to read, and heavy on boilerplate. Adopted from bevyengine#5373, but untangled and rebased to current `bevy/main`. ## Solution 1. Add a method to the `DetectChanges` trait that implements this boilerplate when the appropriate trait bounds are met. 2. Document this minor footgun, and point users to it. ## Changelog * added the `set_if_neq` method to avoid triggering change detection when the new and previous values are equal. This will work on both components and resources. ## Migration Guide If you are manually checking if a component or resource's value is equal to its new value before setting it to avoid triggering change detection, migrate to the clearer and more convenient `set_if_neq` method. ## Context Related to bevyengine#2363 as it avoids triggering change detection, but not a complete solution (as it still requires triggering it when real changes are made). Co-authored-by: Zoey <Dessix@Dessix.net>
ItsDoot
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Feb 1, 2023
# Objective - The doctest for `Mut::map_unchanged` uses a fake function `set_if_not_equal` to demonstrate usage. - Now that bevyengine#6853 has been merged, we can use `Mut::set_if_neq` directly instead of mocking it.
bors bot
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Feb 15, 2023
# Objective While porting my crate `bevy_trait_query` to bevy 0.10, I ran into an issue with the `DetectChangesMut` trait. Due to the way that the `set_if_neq` method (added in #6853) is implemented, you are forced to write a nonsense implementation of it for dynamically sized types. This edge case shows up when implementing trait queries, since `DetectChangesMut` is implemented for `Mut<dyn Trait>`. ## Solution Simplify the generics for `set_if_neq` and add the `where Self::Target: Sized` trait bound to it. Add a default implementation so implementers don't need to implement a method with nonsensical trait bounds.
myreprise1
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Feb 16, 2023
# Objective While porting my crate `bevy_trait_query` to bevy 0.10, I ran into an issue with the `DetectChangesMut` trait. Due to the way that the `set_if_neq` method (added in bevyengine#6853) is implemented, you are forced to write a nonsense implementation of it for dynamically sized types. This edge case shows up when implementing trait queries, since `DetectChangesMut` is implemented for `Mut<dyn Trait>`. ## Solution Simplify the generics for `set_if_neq` and add the `where Self::Target: Sized` trait bound to it. Add a default implementation so implementers don't need to implement a method with nonsensical trait bounds.
myreprise1
pushed a commit
to myreprise1/bevy
that referenced
this pull request
Feb 16, 2023
# Objective While porting my crate `bevy_trait_query` to bevy 0.10, I ran into an issue with the `DetectChangesMut` trait. Due to the way that the `set_if_neq` method (added in bevyengine#6853) is implemented, you are forced to write a nonsense implementation of it for dynamically sized types. This edge case shows up when implementing trait queries, since `DetectChangesMut` is implemented for `Mut<dyn Trait>`. ## Solution Simplify the generics for `set_if_neq` and add the `where Self::Target: Sized` trait bound to it. Add a default implementation so implementers don't need to implement a method with nonsensical trait bounds.
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Objective
Change detection can be spuriously triggered by setting a field to the same value as before. As a result, a common pattern is to write:
This is confusing to read, and heavy on boilerplate.
Adopted from #5373, but untangled and rebased to current
bevy/main.Solution
Changelog
Migration Guide
If you are manually checking if a component or resource's value is equal to its new value before setting it to avoid triggering change detection, migrate to the clearer and more convenient
set_if_neqmethod.Context
Related to #2363 as it avoids triggering change detection, but not a complete solution (as it still requires triggering it when real changes are made).