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``` git subtree add --prefix=docs/ https://github.com/gohugoio/hugoDocs.git master --squash ``` Closes #11925
99 lines
2.5 KiB
Markdown
99 lines
2.5 KiB
Markdown
---
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title: IsDescendant
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description: Reports whether PAGE1 in a descendant of PAGE2.
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categories: []
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keywords: []
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action:
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related:
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- methods/page/Ancestors
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- methods/page/CurrentSection
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- methods/page/FirstSection
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- methods/page/InSection
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- methods/page/IsAncestor
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- methods/page/Parent
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- methods/page/Sections
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returnType: bool
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signatures: [PAGE1.IsDescendant PAGE2]
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---
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{{% include "methods/page/_common/definition-of-section.md" %}}
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With this content structure:
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```text
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content/
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├── auctions/
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│ ├── 2023-11/
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│ │ ├── _index.md
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│ │ ├── auction-1.md
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│ │ └── auction-2.md
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│ ├── 2023-12/
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│ │ ├── _index.md
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│ │ ├── auction-3.md
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│ │ └── auction-4.md
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│ ├── _index.md
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│ ├── bidding.md
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│ └── payment.md
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└── _index.md
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```
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When rendering the "auctions" page:
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```go-html-template
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{{ with .Site.GetPage "/" }}
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{{ $.IsDescendant . }} → true
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{{ end }}
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{{ with .Site.GetPage "/auctions" }}
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{{ $.IsDescendant . }} → false
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{{ end }}
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{{ with .Site.GetPage "/auctions/2023-11" }}
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{{ $.IsDescendant . }} → false
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{{ end }}
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{{ with .Site.GetPage "/auctions/2023-11/auction-2" }}
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{{ $.IsDescendant . }} → false
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{{ end }}
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```
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In the examples above we are coding defensively using the [`with`] statement, returning nothing if the page does not exist. By adding an [`else`] clause we can do some error reporting:
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```go-html-template
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{{ $path := "/auctions/2023-11" }}
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{{ with .Site.GetPage $path }}
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{{ $.IsDescendant . }} → true
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{{ else }}
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{{ errorf "Unable to find the section with path %s" $path }}
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{{ end }}
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```
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## Understanding context
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Inside of the `with` block, the [context] (the dot) is the section `Page` object, not the `Page` object passed into the template. If we were to use this syntax:
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```go-html-template
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{{ with .Site.GetPage "/auctions" }}
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{{ .IsDescendant . }} → true
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{{ end }}
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```
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The result would be wrong when rendering the "auction-1" page because we are comparing the section page to itself.
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{{% note %}}
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Use the `$` to get the context passed into the template.
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{{% /note %}}
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```go-html-template
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{{ with .Site.GetPage "/auctions" }}
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{{ $.IsDescendant . }} → true
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{{ end }}
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```
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{{% note %}}
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Gaining a thorough understanding of context is critical for anyone writing template code.
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{{% /note %}}
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[context]: /getting-started/glossary/#context
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[`with`]: /functions/go-template/with
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[`else`]: /functions/go-template/else
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