35 lines
827 B
Crystal
35 lines
827 B
Crystal
module Spectator
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# Lazily stores a value.
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struct Lazy(T)
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@value : Value(T)?
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# Retrieves the value, if it was previously fetched.
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# On the first invocation of this method, it will yield.
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# The block should return the value to store.
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# Subsequent calls will return the same value and not yield.
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def get(&block : -> T)
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if (existing = @value)
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existing.get
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else
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yield.tap do |value|
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@value = Value.new(value)
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end
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end
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end
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# Wrapper for a value.
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# This is intended to be used as a union with nil.
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# It allows storing (caching) a nillable value.
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private struct Value(T)
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# Creates the wrapper.
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def initialize(@value : T)
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end
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# Retrieves the value.
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def get : T
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@value
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end
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end
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end
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end
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