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75 lines
3 KiB
Markdown
75 lines
3 KiB
Markdown
# cast
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[](https://github.com/spf13/cast/actions/workflows/ci.yaml)
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[](https://pkg.go.dev/mod/github.com/spf13/cast)
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[](https://goreportcard.com/report/github.com/spf13/cast)
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Easy and safe casting from one type to another in Go
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Don’t Panic! ... Cast
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## What is Cast?
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Cast is a library to convert between different go types in a consistent and easy way.
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Cast provides simple functions to easily convert a number to a string, an
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interface into a bool, etc. Cast does this intelligently when an obvious
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conversion is possible. It doesn’t make any attempts to guess what you meant,
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for example you can only convert a string to an int when it is a string
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representation of an int such as “8”. Cast was developed for use in
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[Hugo](https://gohugo.io), a website engine which uses YAML, TOML or JSON
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for meta data.
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## Why use Cast?
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When working with dynamic data in Go you often need to cast or convert the data
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from one type into another. Cast goes beyond just using type assertion (though
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it uses that when possible) to provide a very straightforward and convenient
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library.
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If you are working with interfaces to handle things like dynamic content
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you’ll need an easy way to convert an interface into a given type. This
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is the library for you.
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If you are taking in data from YAML, TOML or JSON or other formats which lack
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full types, then Cast is the library for you.
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## Usage
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Cast provides a handful of To_____ methods. These methods will always return
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the desired type. **If input is provided that will not convert to that type, the
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0 or nil value for that type will be returned**.
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Cast also provides identical methods To_____E. These return the same result as
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the To_____ methods, plus an additional error which tells you if it successfully
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converted. Using these methods you can tell the difference between when the
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input matched the zero value or when the conversion failed and the zero value
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was returned.
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The following examples are merely a sample of what is available. Please review
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the code for a complete set.
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### Example ‘ToString’:
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cast.ToString("mayonegg") // "mayonegg"
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cast.ToString(8) // "8"
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cast.ToString(8.31) // "8.31"
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cast.ToString([]byte("one time")) // "one time"
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cast.ToString(nil) // ""
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var foo interface{} = "one more time"
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cast.ToString(foo) // "one more time"
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### Example ‘ToInt’:
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cast.ToInt(8) // 8
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cast.ToInt(8.31) // 8
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cast.ToInt("8") // 8
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cast.ToInt(true) // 1
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cast.ToInt(false) // 0
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var eight interface{} = 8
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cast.ToInt(eight) // 8
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cast.ToInt(nil) // 0
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