A simple NSLayoutConstraint expression parser for more readable autolayout code. By Marco Arment and released under the MIT license.
Apple’s visual format syntax is helpful, but it cannot express all types of autolayout constraints, and it’s not ideal for simple values. Creating NSLayoutConstraints manually is more powerful and covers all possibilities, but is extremely verbose and hard to read.
CompactConstraint brings compact, readable syntax to creating NSLayoutConstraints manually. In short, rather than writing Cocoa autolayout constraints like this:
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:emailLabel
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationGreaterThanOrEqual
toItem:emailField
attribute:NSLayoutAttributeLeft
multiplier:1.0f
constant:0.0f]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:spinner
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:logInButton
attribute:NSLayoutAttributeRight
multiplier:1.0f
constant:10.0f]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:preview
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:preview
attribute:NSLayoutAttributeWidth
multiplier:0.625f
constant:0.0f]];
CompactConstraint lets you write them like this:
[self.view addCompactConstraint:@"emailLabel.left >= emailField.left"
metrics:metrics
views:views];
[self.view addCompactConstraint:@"spinner.left = logInButton.right + 10"
metrics:metrics
views:views];
[self.view addCompactConstraint:@"preview.height = preview.width / 1.6"
metrics:metrics
views:views];
Or this:
[self.view addCompactConstraints:@[@"emailLabel.left >= emailField.left",
@"spinner.left = logInButton.right + 10",
@"preview.height = preview.width / 1.6"]
metrics:metrics
views:views];