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93 lines
2.5 KiB
Markdown
93 lines
2.5 KiB
Markdown
---
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title: default
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description: Allows setting a default value that can be returned if a first value is not set.
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qref: "Returns a default value if a value is not set when checked."
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godocref:
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date: 2017-02-01
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publishdate: 2017-02-01
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lastmod: 2017-02-01
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keywords: [defaults]
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categories: [functions]
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menu:
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docs:
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parent: "functions"
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toc:
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signature: ["default DEFAULT INPUT"]
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workson: []
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hugoversion:
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relatedfuncs: []
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deprecated: false
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draft: false
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aliases: [/functions/default/]
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needsexamples: false
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---
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`default` checks whether a given value is set and returns a default value if it is not. *Set* in this context means different things depending on date type:
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* non-zero for numeric types and times
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* non-zero length for strings, arrays, slices, and maps
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* any boolean or struct value
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* non-nil for any other types
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`default` function examples reference the following content page:
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{{< code file="content/posts/default-function-example.md" >}}
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---
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title: Sane Defaults
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seo_title:
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date: 2017-02-18
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font:
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oldparam: The default function helps make your templating DRYer.
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newparam:
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---
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{{< /code >}}
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`default` can be written in more than one way:
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```
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{{ index .Params "font" | default "Roboto" }}
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{{ default "Roboto" (index .Params "font") }}
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```
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Both of the above `default` function calls return `Roboto`.
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A `default` value, however, does not need to be hard coded like the previous example. The `default` value can be a variable or pulled directly from the front matter using dot notation:
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{{< code file="variable-as-default-value.html" nocopy="true" >}}
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{{$old := .Params.oldparam }}
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<p>{{ .Params.newparam | default $old }}</p>
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{{< /code >}}
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Which would return:
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```
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<p>The default function helps make your templating DRYer.</p>
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```
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And then using dot notation
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{{< code file="dot-notation-default-value.html" >}}
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<title>{{ .Params.seo_title | default .Title }}</title>
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{{< /code >}}
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Which would return
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{{< output file="dot-notation-default-return-value.html" >}}
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<title>Sane Defaults</title>
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{{< /output >}}
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The following have equivalent return values but are far less terse. This demonstrates the utility of `default`:
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Using `if`:
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{{< code file="if-instead-of-default.html" nocopy="true" >}}
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<title>{{if .Params.seo_title}}{{.Params.seo_title}}{{else}}{{.Title}}{{end}}</title>
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=> Sane Defaults
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{{< /code >}}
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Using `with`:
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{{< code file="with-instead-of-default.html" nocopy="true" >}}
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<title>{{with .Params.seo_title}}{{.}}{{else}}{{.Title}}{{end}}</title>
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=> Sane Defaults
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{{< /code >}}
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