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41 lines
584 B
Markdown
41 lines
584 B
Markdown
# Singleton Pattern
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Singleton creational design pattern restricts the instantiation of a type to a single object.
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## Implementation
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```go
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package singleton
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type singleton map[string]string
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var once sync.Once
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var instance *singleton
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func New() *singleton {
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once.Do(func() {
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instance = make(singleton)
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})
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return instance
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}
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```
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## Usage
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```go
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s := singleton.New()
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s["this"] = "that"
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s2 := singleton.New()
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fmt.Println("This is ", s2["this"])
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// This is that
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```
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## Rules of Thumb
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- Singleton pattern represents a global state and most of the time reduces testability.
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