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https://github.com/tagomoris/deferral
Golang-style defer in Ruby
https://github.com/tagomoris/deferral
Last synced: 16 days ago
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Golang-style defer in Ruby
- Host: GitHub
- URL: https://github.com/tagomoris/deferral
- Owner: tagomoris
- License: mit
- Created: 2018-02-24T08:28:09.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2019-01-05T02:42:29.000Z (almost 6 years ago)
- Last Synced: 2024-04-15T02:58:22.747Z (7 months ago)
- Language: Ruby
- Homepage:
- Size: 29.3 KB
- Stars: 176
- Watchers: 8
- Forks: 7
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
Awesome Lists containing this project
README
# Deferral - introduce golang style "defer" in Ruby
```ruby
# gem install deferral
require "deferral/toplevel"
using Deferral::TopLevel
# it makes "defer" without module name available everywhere in this file
def my_method_name
# ...
file = File.open("my_file", "r")
defer { file.close }
file.write "data..."
# ...
end # `file.close` is called at the end of method (even when exception thrown)
# or end of blocks
def my_method_name(list)
# ...
list.each do |item|
file = File.open(item, "r")
defer { file.close }
file.write "data..."
# ...
end # `file.close` is called at the end of block
end
# "deferral" imports `Deferral.defer`, not to inject top-level methods widely.
require "deferral"
# or enable everywhere! (DANGER!)
require "deferral/kernel_ext"
```
This gem provides a feature to release resources safely, using golang style `defer` method.
`Deferral.defer` method does:
* accept a block argument to execute at the end of caller scope
* execute specified blocks in reverse order when getting out from specified scope
Resource release blocks are called even when any exception occurs.
See also [with_resources gem](https://github.com/tagomoris/with_resources) for try-with-resources style resource allocator.
### Disclosure
This library is a kind of PoC to introduce safe resource allocation in Ruby world. Take care about using this library in your production environment.
This library uses/enables TracePoint, and it may collapse optimizations of your Ruby runtime.
## API
* `Deferral.defer(&block)`
This method registers a block to be called at the end of caller scope (end of method or block). Registered blocks will be called in reverse order (LIFO: last-in, first-out) when this method is called twice or more in a scope.
### Introduce `defer` to top-level namespace
Top-level `defer` is available via 2 different ways. One is using Refinements, another is modifying `Kernel` in open-class way.
```ruby
require "deferral/toplevel"
using Deferral::TopLevel
def my_method
f = AnyResource.new
defer { f.close }
# ...
end
```
Refinements is a feature of Ruby to apply Module modification in just a file (by `using` statement).
`using Deferral::TopLevel` introduces top level `defer` in safer way than modifying `Kernel`.
```ruby
require "deferral/kernel_ext"
# now, "defer" is available everywhere...
```
Requiring `deferral/kernel_ext` modifies `Kernel` module globally to add `deferral`. It's not recommended in most cases.
* * * * *
## Authors
* Satoshi Tagomori
## License
MIT (See License.txt)