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Stevia 🍃
Elegant view layout for iOS
layout([
100,
|-email-| ~ 80,
8,
|-password-| ~ 80,
"",
|login| ~ 80,
0
])Why
Because nothing holds more truth than pure code
Xibs and storyboards are heavy, hard to maintain, hard to merge.
They split the view concept into 2 separate files making debugging a nightmare
There must be a better way
How
By creating a tool that makes Auto layout code finally readable by a human being.
By coupling it with live code injection such as injectionForXcode we can design views in real time
View layout becomes fun, concise, maintainable and dare I say, beautiful
What
- Auto Layout DSL
- Pure Swift
- Simple, this is just NSLayoutConstraint shortcuts, pure UIKit code, no voodoo magic
- Chainable api
Advantages of Stevia 🍃 over Xibs or storyboards
- No more constraints hell in Interface builder.
- No more debugging in Interface builder toggling checkboxes.
- The view code is not split between 2 files anymore
- What you see is what you get, your view code is in one place, there is no hidden logic elsewere (in the xib)
- No more referencing Storyboards or Xibs by their names "ProfileStoryboard". We all know strings are bad identifiers.
- Clear view Hierarchy
- Live reload, WHAT YOU SEE IS WHAT YOU GET
- Events are a breeze
- Code views Faster
- No more XML (Thank God!)
- Better readability 1000lines XML file vs. 30lines code
- Readable constraints (they actually look like the layout itself \o/)
- Horizontal & vertical layout can be described at the same time
- Styles are well separated, concise, reusable and can be composed
- Content like text, placeholders are easier to visualize
Real life example : a classic Login View
Before (Native Autolayout)
class LoginViewNative:UIView {
let email = UITextField()
let password = UITextField()
let login = UIButton()
convenience init() {
self.init(frame:CGRectZero)
backgroundColor = .whiteColor()
addSubview(email)
addSubview(password)
addSubview(login)
email.translatesAutoresizingMaskIntoConstraints = false
password.translatesAutoresizingMaskIntoConstraints = false
login.translatesAutoresizingMaskIntoConstraints = false
addConstraint(NSLayoutConstraint(
item: email,
attribute: .Left,
relatedBy: .Equal,
toItem: self,
attribute: .Left,
multiplier: 1,
constant: 8)
)
addConstraint(NSLayoutConstraint(
item: email,
attribute: .Right,
relatedBy: .Equal,
toItem: self,
attribute: .Right,
multiplier: 1,
constant: -8)
)
addConstraint(NSLayoutConstraint(
item: password,
attribute: .Left,
relatedBy: .Equal,
toItem: self,
attribute: .Left,
multiplier: 1,
constant: 8)
)
addConstraint(NSLayoutConstraint(
item: password,
attribute: .Right,
relatedBy: .Equal,
toItem: self,
attribute: .Right,
multiplier: 1,
constant: -8)
)
addConstraint(NSLayoutConstraint(
item: login,
attribute: .Left,
relatedBy: .Equal,
toItem: self,
attribute: .Left,
multiplier: 1,
constant: 0)
)
addConstraint(NSLayoutConstraint(
item: login,
attribute: .Right,
relatedBy: .Equal,
toItem: self,
attribute: .Right,
multiplier: 1,
constant: 0)
)
for b in [email, password, login] {
addConstraint(NSLayoutConstraint(
item: b,
attribute: .Height,
relatedBy: .Equal,
toItem: nil,
attribute: .NotAnAttribute,
multiplier: 1,
constant: 80)
)
}
addConstraint(NSLayoutConstraint(
item: email,
attribute: .Top,
relatedBy: .Equal,
toItem: self,
attribute: .Top,
multiplier: 1,
constant: 100)
)
addConstraint(NSLayoutConstraint(
item:email,
attribute: .Bottom,
relatedBy: .Equal,
toItem: password,
attribute: .Top,
multiplier: 1,
constant: -8)
)
addConstraint(NSLayoutConstraint(
item: login,
attribute: .Bottom,
relatedBy: .Equal,
toItem: self,
attribute: .Bottom,
multiplier: 1,
constant: 0)
)
email.placeholder = "Email"
email.borderStyle = .RoundedRect
email.autocorrectionType = .No
email.keyboardType = .EmailAddress
email.font = UIFont(name: "HelveticaNeue-Light", size: 26)
email.returnKeyType = .Next
password.placeholder = "Password"
password.borderStyle = .RoundedRect
password.font = UIFont(name: "HelveticaNeue-Light", size: 26)
password.secureTextEntry = true
password.returnKeyType = .Done
login.setTitle("Login", forState: .Normal)
login.backgroundColor = .lightGrayColor()
login.addTarget(self, action: "loginTapped", forControlEvents: .TouchUpInside)
login.setTitle(NSLocalizedString("Login", comment: ""), forState: .Normal)
}
func loginTapped() {
//Do something
}
}With Stevia 🍃
class LoginViewStevia:UIView {
let email = UITextField()
let password = UITextField()
let login = UIButton()
convenience init() {
self.init(frame:CGRectZero)
backgroundColor = .whiteColor()
sv([
email.placeholder("Email").style(fieldStyle), //.style(emailFieldStyle),
password.placeholder("Password").style(fieldStyle).style(passwordFieldStyle),
login.text("Login").style(buttonSytle).tap(loginTapped)
])
layout([
100,
|-email-| ~ 80,
8,
|-password-| ~ 80,
"",
|login| ~ 80,
0
])
}
func fieldStyle(f:UITextField) {
f.borderStyle = .RoundedRect
f.font = UIFont(name: "HelveticaNeue-Light", size: 26)
f.returnKeyType = .Next
}
func passwordFieldStyle(f:UITextField) {
f.secureTextEntry = true
f.returnKeyType = .Done
}
func buttonSytle(b:UIButton) {
b.backgroundColor = .lightGrayColor()
}
func loginTapped() {
//Do something
}
}Number of lines From 144 -> 57 ( ~ divided by 2.5)
Number of characters From 4231 -> 1338 ( ~ divided by 3)
Write 3 times less code that is actually 10X more expressive and maintainable <3
Live Reload
You can even enable LiveReload during your development phase!
Stevia + InjectionForXCode = <3 (WhoNeedsReactNative??)
In order to support live reload with InjectionForXCode, we simply need to tell our ViewController to rebuild a view after an injection occured.
on("INJECTION_BUNDLE_NOTIFICATION") {
self.v = CodeRequestView()
self.view = self.v
}Currently InjectionForXcode doesn't seem to swizzle "init" methods for some reason. So we have to move our view code in another methods
convenience init() {
self.init(frame:CGRectZero)
//View code
}Becomes
convenience init() {
self.init(frame:CGRectZero)
render()
}
func render() {
//View code
}
And Voila :)
Installation
Manual
Copy Stevia source files to your XCode project
Carthage
github "s4cha/Stevia"
##Rationale behind the project
On the Yummypets app, we needed to deal with looooooots of views.
After trying different methods for building views (Xibs, Storyboards, Splitting Storyboards, React Native even(!).
We found that coding views programmatically was the best solution for us.
But coding views programmatically had its issues too : UIKit exposes an imperative verbose API, and it's really easy to create a mess with it.
That's why we created Stevia.
Contributors
YannickDot, S4cha, Damien, Snowcraft
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Stevia