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36 lines
1.2 KiB
Markdown
36 lines
1.2 KiB
Markdown
# Format A Hash Into A String Template
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The `%` method as defined by `String`
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([`String#%`](https://ruby-doc.org/core-3.0.0/String.html#method-i-25)) allows
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you to format (interpolate) an object or array of values into a string. That
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string needs to contain template markers for where the values should go.
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Here is an example of folding an array of values into a string with [`%s`
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format
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specifier](https://docs.ruby-lang.org/en/master/format_specifications_rdoc.html#label-Specifier+s):
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```ruby
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> User = Struct.new(:id)
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=> User
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> user1 = User.new(123)
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=> #<struct User id=123>
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> "%s ID: %s" % [user1.class.to_s, user1.id]
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=> "User ID: 123"
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```
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Or perhaps more usefully for a string that acts as a template, you can used
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named specifiers that correspond to hash keys:
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```ruby
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> template = "You paid %{formatted_price} for %{product}. Enjoy your purchase!"
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=> "You paid %{formatted_price} for %{product}. Enjoy your purchase!"
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> data = { product: "Ruby Explained™", formatted_price: "$38.99" }
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=> {:product=>"Ruby Explained™", :formatted_price=>"$38.99"}
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> template % data
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=> "You paid $38.99 for Ruby Explained™. Enjoy your purchase!"
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```
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[source](https://hashrocket.com/blog/posts/using-a-hash-of-data-for-string-replacement-in-ruby)
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