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https://github.com/dhruvrajvanshi/crystal-futures
Future type implementation for Crystal language
https://github.com/dhruvrajvanshi/crystal-futures
Last synced: about 2 months ago
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Future type implementation for Crystal language
- Host: GitHub
- URL: https://github.com/dhruvrajvanshi/crystal-futures
- Owner: dhruvrajvanshi
- License: mit
- Created: 2015-06-21T17:46:17.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2017-04-10T11:23:40.000Z (over 7 years ago)
- Last Synced: 2024-08-01T02:25:28.020Z (4 months ago)
- Language: Crystal
- Homepage:
- Size: 46.9 KB
- Stars: 57
- Watchers: 4
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-crystal - crystal-futures - Future type implementation (Processes and Threads)
- awesome-crystal - crystal-futures - Future type implementation (Processes and Threads)
README
# crystal-futures [](https://travis-ci.org/dhruvrajvanshi/crystal-futures)
Futures provide a nice way to reason about performing many operations in parallel– in an efficient and non-blocking way. The idea is simple, a Future is a sort of a placeholder object that you can create for a result that does not yet exist. Generally, the result of the Future is computed concurrently and can be later collected. Composing concurrent tasks in this way tends to result in faster, asynchronous, non-blocking parallel code.
** Source : http://docs.scala-lang.org/overviews/core/futures.html
## Usage
```crystal
require "futures"
include Futures
# Create a new future
a = Future.new do
someTimeConsumingOperation()
end
# Register a callback on successful operation
a.on_success do |val|
doSomethingWithResult val
end
a.on_failure do |err|
raise err
end
# Or handle both cases in one callback
a.on_complete do |result|
try = result.get
case try
when Success
puts try.get
when Failure
raise try.error
end
end
# Or block until future completes
val = a.get
# compose new Futures from existing ones
b = a.map do |val|
"String : " + val
end
b.get
```
### Sequencing
Future implements [crz](https://github.com/dhruvrajvanshi/crz) ```Monad``` interface
which means you can call bind on it to sequence multiple actions.
```crystal
def get_first_value
Future.new do
# get a value from network
...
end
end
def get_second_value(first_value)
Future.new do
# get another value based on
# the first value
...
end
end
f = get_first_value.bind do |first_value|
get_second_value(first_value)
end
f.get # => second value
```
In case of multiple actions in sequence, nested binds can become
tedious and error prone. Use the crz ```mdo``` macro to flatten
nested binds
```crystal
mdo({
first <= get_first_value,
second <= get_second_value(first),
third <= get_third_value(first, second),
Future.of(third)
})
```
Make sure the last line of mdo is wrapped in a future using
Future.of or ```Future.new { value }```.
Note that ```<=``` only works on Futures not on regular values
i.e. ```get_first_value```, ```get_second_value```, ```get_third_value```
should return Futures.
You can make normal assignments from regular values inside mdo blocks too.
```crystal
mdo({
x <= some_async_op,
a = x + 23,
...
})
```
## Documentation
[Link](http://dhruvrajvanshi.github.io/crystal-futures/)