TATLayout: An Objective-C repository from cromandini

An expressive, simple yet powerful way for coding layout constraints in iOS.

TATLayout aims to reduce considerably the amount of lines of code used when coding layout constraints in iOS. It provides a high level API to layout constraints that makes your layout code easier to read, mantain and modify dynamically.

Features:

Category in NSLayoutConstraint providing a factory method for creating constraints using a linear equation format string.
Category in NSLayoutConstraint providing methods for activation and deactivation that can be used in iOS 6+ but uses iOS 8 when available, using feature detection.
A couple of helper methods useful for working with layouts.

Requirements

iOS 6.0+

Getting it

TATLayout is available through CocoaPods and as a static library. Check out the Wiki for detailed installation steps.

Usage

Check out the documentation for a comprehensive look at all of the APIs available in TATLayout.

#import <TATLayout/TATLayout.h>

UIView *view1 = [UIView new];
UIView *view2 = [UIView new];
UILabel *label = [UILabel new];
NSDictionary *metrics = @{@"multiplier": @0.5, @"constant": @50, @"priority": @751};
NSDictionary *views = NSDictionaryOfVariableBindings(view1, view2, label);

TATDisableAutoresizingConstraintsInViews(view1, view2, label);


// Creating constraints with equation format strings:

NSLayoutConstraint *c;

// view1 width is equal to 100 points
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view1.width == 100" metrics:nil views:views];

// view1 height is equal to 2 times its width
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view1.height == view1.width * 2" metrics:nil views:views];

// view1 center x is equal to its superview's center x
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view1.centerX == superview.centerX" metrics:nil views:views];

// view1 top is equal to its superview's top plus 50 points
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view1.top == superview.top + constant" metrics:metrics views:views];

// view1 bottom is less than or equal to its superview's bottom with a priority of 251
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view1.bottom <= superview.bottom @251" metrics:nil views:views];

// view1 bottom is greater than or equal to view2's bottom with a priority of 751
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view1.bottom >= view2.bottom @priority" metrics:metrics views:views];

// view2 top is greater than or equal to three quarters of view1's top plus 50 points with a priority of 500
c = [NSLayoutConstraint tat_constraintWithEquationFormat:@"view2.top >= view1.top * 0.75 + 50 @500" metrics:nil views:views];


// Multiple constraints can be created at once:

NSArray *constraints = [tat_constraintsWithEquationFormats:@[@"view2.leading == view1.trailing" // view2 leading is equal to view1's trailing
                                                             @"view2.trailing == superview.trailing" // view2 trailing is equal to its superview's trailing
                                                             @"view2.height == view1.height * multiplier" // view2 height is equal to half the view1's height
                                                             @"label.baseline == view1.centerY" // label baseline is equal to view1's centerY
                                                             @"label.centerX == view1.centerX"] // label is x centered with view1
                                                   metrics:metrics views:views];


// Activating and deactivating constraints:

// Single (uses iOS 8 built-in when available)
c.tat_active = YES;
c.tat_active = NO;

// Multiple (uses iOS 8 built-in when available)
[NSLayoutConstraint tat_activateConstraints:constraints];
[NSLayoutConstraint tat_deactivateConstraints:constraints];


// Creating and activating constraints in the same operation:

[NSLayoutConstraint tat_activateConstraintWithEquationFormat:@"label.leading == view1.trailing" metrics:metrics views:views];

[NSLayoutConstraint tat_activateConstraintsWithEquationFormats:@[@"label.leading == view1.trailing"
                                                                @"label.trailing == view2.leading",
                                                                @"label.baseline == view1.centerY"]
                                                      metrics:metrics views:views];

[NSLayoutConstraint tat_activateConstraintsWithVisualFormat:@"H:|[view1][label][view2]|" options:NSLayoutFormatAlignAllTop metrics:metrics views:views];

Example app

Try out the example app by opening TATLayout.xcworkspace and running TATLayoutExample scheme. If you haven't cloned the project you can use CocoaPods try command:

$ pod try TATLayout

Unit Tests

TATLayout is driven by unit testing. In order to run the tests, you must install the testing dependencies via CocoaPods:

$ pod install

Once testing dependencies are installed, open TATLayout.xcworkspace in Xcode, make sure you have selected TATLayoutExample scheme and hit command+U.

Documentation

The documentation is available online through CocoaDocs.

Credits

TATLayout uses Kiwi for unit testing.

This project is under the MIT license.

cromandini/TATLayout