https://github.com/zillow/combine-ergonomics
https://github.com/zillow/combine-ergonomics
Last synced: 8 months ago
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- Host: GitHub
- URL: https://github.com/zillow/combine-ergonomics
- Owner: zillow
- License: apache-2.0
- Created: 2022-01-07T21:25:06.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2022-01-10T14:50:51.000Z (over 4 years ago)
- Last Synced: 2024-04-14T05:27:29.303Z (about 2 years ago)
- Language: Swift
- Size: 24.8 MB
- Stars: 1
- Watchers: 8
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
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README
# CombineErgonomics
This package contains useful extensions for Combine that make it easier to develop with and test.
To add this package to your project, go into your project settings and add the url `https://github.com/zillow/combine-ergonomics.git` to your Swift Packages. To use it, just `import CombineErgonomics` at the top of your swift files. To use the `XCTestCase` extensions, `import CombineErgonomicsTestExtensions`.
## Benefits
### Attach handlers to Publishers
CombineErgonomics makes it easier to dispatch background tasks and handle their errors, with syntax inspired by [PromiseKit](https://github.com/mxcl/PromiseKit). For example, consider this class that facilitates login:
```swift
import Combine
class LoginHelper {
var store = Set()
func login() {
let future = Future { promise in
// network call to log in
}
future.subscribe(on: DispatchQueue.global())
.sink { completion in
if case .failure(let error) = completion {
// handle error
}
} receiveValue: { user in
// handle user logged in, i.e. update UI
}
.store(in: &store)
}
}
```
Can be reduced to:
```swift
import Combine
import CombineErgonomics
class LoginHelper {
func login() {
let future = Future { promise in
// network call to log in
}
future.done { user in
// handle user logged in, i.e. update UI
}.catch { error in
//handle error
}
}
}
```
### Chain together multiple Futures
Rather than using a chain of `Combine.FlatMap`, `Future`s can be neatly chained using the `.then` method.
```swift
import Combine
import CombineErgonomics
class LoginHelper {
func login() {
let future = Future { promise in
// network call to log in
}
future.then { user -> Future in
return ProfileImageHelper.fetchProfileImage(for: user)
}.done { profileImage in
// update UI with new profile image
}.catch { error in
// handle error
}
}
}
```
### Unit test published values
One common pattern used in reactive programming, and especially in MVVM app architecture is binding the view's state to observable values on a view model. Testing these view model properties can be a bit messy when asynchronous code is involved.
```swift
import Combine
import CombineErgonomics
import XCTest
class LoginViewModel {
@Published var user: User?
@Published var isLoading = false
func login() {
self.isLoading = true
NetworkHelper.login().done { user in
self.user = user
}.finally {
self.isLoading = false
}
}
}
class LoginViewModelTests: XCTestCase {
func testLogin() {
let loginViewModel = LoginViewModel()
let loadingExpectation = XCTestExpectation(description: "View model starts loading, then finishes")
loadingExpectation.expectedFulfillmentCount = 2
var values: [Bool] = []
let cancellable = loginViewModel.$isLoading.dropFirst(1).sink { isLoading in
expectation.fulfill()
values.append(isLoading)
}
loginViewModel.login()
wait(for: [loadingExpectation], timeout: 1)
XCTAssertEqual(values, [true, false])
XCTAssertNotNil(loginViewModel.user)
}
}
```
With the test extensions, the login test case can be reduced to something much more readable, allowing you to focus on the actual logic being tested.
```swift
import CombineErgonomicsTestExtensions
import XCTest
class LoginHelperTests: XCTestCase {
func testLogin() {
let loginViewModel = LoginViewModel()
let values = values(for: loginViewModel.$isLoading, expectedNumber: 2) {
loginViewModel.login()
}
XCTAssertEqual(values, [true, false])
XCTAssertNotNil(loginViewModel.user)
}
}
```
## Documentation
You can find [more detailed documentation here](http://combine-ergonomics-framework-docs.s3-website-us-east-1.amazonaws.com/).