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psi_elements.md: improve "how do i get..." section

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Karol Lewandowski 2022-03-25 09:26:13 +01:00
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topics/basics/architectural_overview/psi_elements.md
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[//]: # (title: PSI Elements)
<!-- Copyright 2000-2022 JetBrains s.r.o. and other contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file. -->
<!-- Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license. -->
A PSI (Program Structure Interface) file represents a hierarchy of PSI elements (so-called _PSI trees_).
A single [PSI file](psi_files.md) (itself being a PSI element) may expose several PSI trees in specific programming languages (see [](file_view_providers.md)).
@ -13,14 +13,11 @@ The [`PsiElement`](upsource:///platform/core-api/src/com/intellij/psi/PsiElement
## How do I get a PSI element?
* From an Action: `AnActionEvent.getData(CommonDataKeys.PSI_ELEMENT)`.
Note: if an editor is currently open and the element under caret is a [reference](psi_references.md), this will return the result of resolving the reference.
This may or may not be what you need.
* From a file by offset: `PsiFile.findElementAt()`.
Note: this returns the lowest level element ("leaf") at the specified offset, normally a lexer token.
Most likely, you should use `PsiTreeUtil.getParentOfType()` to find the element you really need.
* By iterating through a PSI file: using a [`PsiRecursiveElementWalkingVisitor`](upsource:///platform/core-api/src/com/intellij/psi/PsiRecursiveElementWalkingVisitor.java).
* By resolving a [reference](psi_references.md): `PsiReference.resolve()`
| Context | API |
|----------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| [Action](basic_action_system.md) | [`AnActionEvent.getData(CommonDataKeys.PSI_ELEMENT)`](upsource:///platform/editor-ui-api/src/com/intellij/openapi/actionSystem/AnActionEvent.java)<br/>Note: If an editor is currently open and the element under caret is a [reference](psi_references.md), this will return the result of resolving the reference. |
| [PSI File](psi_files.md) | [`PsiFile.findElementAt(offset)`](upsource:///platform/core-api/src/com/intellij/psi/PsiFile.java) - This returns a leaf element at the specified offset, normally a lexer token. Use `PsiTreeUtil.getParentOfType()` to find the element of the exact type.<br/>[`PsiRecursiveElementWalkingVisitor`](upsource:///platform/core-api/src/com/intellij/psi/PsiRecursiveElementWalkingVisitor.java) |
| [Reference](psi_references.md) | [`PsiReference.resolve()`](upsource:///platform/core-api/src/com/intellij/psi/PsiReference.java) |
## What can I do with PSI elements?