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88 lines
2.1 KiB
Markdown
88 lines
2.1 KiB
Markdown
---
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title: compare.Default
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linkTitle: 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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categories: [functions]
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keywords: []
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menu:
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docs:
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parent: functions
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function:
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aliases: [default]
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returnType: any
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signatures: [compare.Default DEFAULT INPUT]
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relatedFunctions:
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- compare.Conditional
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- compare.Default
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aliases: [/functions/default]
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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 the data 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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```go-html-template
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{{ .Params.font | default "Roboto" }}
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{{ default "Roboto" .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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```go-html-template
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{{ $old := .Params.oldparam }}
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<p>{{ .Params.newparam | default $old }}</p>
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```
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Which would return:
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```html
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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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```go-html-template
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<title>{{ .Params.seo_title | default .Title }}</title>
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```
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Which would return
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```html
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<title>Sane Defaults</title>
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```
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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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```go-html-template
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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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```
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Using `with`:
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```go-html-template
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<title>{{ with .Params.seo_title }}{{ . }}{{ else }}{{ .Title }}{{ end }}</title>
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=> Sane Defaults
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```
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