awesome-patterns/concurrency/generator.md
2016-10-03 16:55:45 +03:00

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Markdown

# Generator Pattern
[Generators](https://en.wikipedia.org/wiki/Generator_(computer_programming)) yields a sequence of values one at a time.
## Implementation
```go
func Count(start int, end int) chan int {
ch := make(chan int)
go func(ch chan int) {
for i := start; i < end ; i++ {
// Blocks on the operation
ch <- i
}
close(ch)
}(ch)
return ch
}
```
## Usage
```go
fmt.Println("No bottles of beer on the wall")
for i := range Count(1, 99) {
fmt.Println("Pass it around, put one up,", i, "bottles of beer on the wall")
// Pass it around, put one up, 1 bottles of beer on the wall
// Pass it around, put one up, 2 bottles of beer on the wall
// ...
// Pass it around, put one up, 99 bottles of beer on the wall
}
fmt.Println(100, "bottles of beer on the wall")
```