Guard conditions in when expressions #4417
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AlejandraPedroza
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docs/topics/coding-conventions.md
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| @@ -999,6 +999,24 @@ when (x) { | |||
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| Prefer using `when` if there are three or more options. | |||
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| ### Guard conditions in when expression | |||
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| Prefer using parentheses when combining multiple boolean expressions in `when` expressions or statements with [guard conditions](control-flow.md#guard-conditions-in-when-expressions): | |||
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Actually, I don't like "Prefer" in the beginning of that sentence.
Can we omit it? Like "Use parentheses ..."?
docs/topics/control-flow.md
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| > | ||
| {type="warning"} | ||
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| Starting from Kotlin 2.1, you can use guard conditions in `when` expressions or statements with a subject. |
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Actually, we try to avoid such phrases since our documentation reflects the latest state of the language.
docs/topics/control-flow.md
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| Guard conditions allow you to include more than one condition to the branches of a `when` expression, making complex control flow more explicit and concise. | ||
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| To include a guard condition in a branch, place the guard condition after the primary condition, separated by `if`: |
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place it.
Will it work?
Just to avoid repetition.
docs/topics/control-flow.md
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| The code in a branch with a guard condition runs only if both the primary condition and the guard condition evaluate to true. | ||
| If the primary condition does not match, the guard condition is not evaluated. | ||
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| If you use guard conditions in `when` statements without an `else` branch, if none of the conditions matches, none of the branches is executed. |
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I'd like to avoid "if" doubling.
Can we say: If you use guard conditions in when statements without an else branch, and none of the conditions match, no branches are executed.
docs/topics/control-flow.md
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| If you use guard conditions in `when` statements without an `else` branch, if none of the conditions matches, none of the branches is executed. | ||
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| Otherwise, if you use guard conditions in `when` expressions without an `else` branch, the compiler requires you to declare all the possible cases (to avoid runtime errors). |
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I guess that "to avoid runtime errors" could be mentioned without parentheses.
docs/topics/control-flow.md
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| ``` | ||
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| Combine multiple guard conditions within a single branch using the boolean operators `&&` (AND) or `||` (OR). | ||
| It is [strongly recommended](coding-conventions.md#guard-conditions-in-when-expression) to use parentheses around the boolean expressions to avoid confusion: |
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How about to rephrase it as
"To avoid confusion, use parentheses ...". Or is it too strong?
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Left it as "Use parentheses around the boolean expressions to..." to make it action-oriented.
docs/topics/control-flow.md
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| > To enable guard conditions in Gradle, run the following command: | ||
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| > `kotlin.compilerOptions.freeCompilerArgs.add("-Xwhen-guards")t` |
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Shouldn't the option be added to the build.gradle.kts file?
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True. Great catch!
This PR adds information about Guard conditions in when expressions and how to use them.
Co-authored-by: Alejandro Serrano <[email protected]>
Co-authored-by: Alejandro Serrano <[email protected]>
AlejandraPedroza
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This PR adds information about Guard conditions in when expressions and how to use them.