Parus

Parus is a small objective-c DSL for AutoLayout in code.

Features

• It is easy to create constraints - just like writing a sentence;
• More compact and semantical than usual NSAutoLayout;
• Flexibility in creating constraints - you specify only parameters that you need;
• Autocomplete rocks!

Usage

Single constraint

NSLayoutConstraint:

[NSLayoutConstraint constraintWithItem:view
                             attribute:NSLayoutAttributeLeft
                             relatedBy:NSLayoutRelationEqual
                                toItem:superview
                             attribute:NSLayoutAttributeLeft
                            multiplier:2.0
                              constant:10];

Using Parus:

PVLeftOf(view).equalTo.leftOf(superview).multipliedTo(2).plus(10).asConstraint;

Using default values make it even shorter:

[NSLayoutConstraint constraintWithItem:view
                             attribute:NSLayoutAttributeLeft
                             relatedBy:NSLayoutRelationEqual
                                toItem:nil
                             attribute:NSLayoutAttributeNotAnAttribute
                            multiplier:1.0
                              constant:10];

PVLeftOf(view).equalTo.constant(10).asConstraint;

Visual Formatting Language (VFL)

Simple VFL constraints:

[NSLayoutConstraint constraintsWithVisualFormat:@"|-padding-[view]-padding-|"
                                        options:(NSLayoutFormatAlignAllTop | 
                                                 NSLayoutFormatDirectionLeadingToTrailing)
                                        metrics:@{@"padding" : @20}
                                          views:NSDictionaryOfVariableBindings(view)];

PVVFL(@"|-padding-[view]-padding-|").alignAllTop.fromLeadingToTrailing.withViews(NSDictionaryOfVariableBindings(view)).metrics(@{@"padding": @20}).asArray;

With special masks and defaults:

[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[view1][view2][view3]|"
                                        options:(NSLayoutFormatAlignAllLeft | 
                                                 NSLayoutFormatAlignAllRight)
                                        metrics:nil
                                          views:NSDictionaryOfVariableBindings(view1, view2, view3)];

PVVFL(@"V:|[view1][view2][view3]|").alignAllLeftAndRight.withViews(NSDictionaryOfVariableBindings(view1, view2, view3)).asArray;

Groups

There is available feature that helps you group constraints and produce even less code. Enjoy!

[someView addConstraint:[NSLayoutConstraint constraintWithItem:view
                           						     attribute:NSLayoutAttributeLeft
                             						 relatedBy:NSLayoutRelationEqual
                                						toItem:nil
                             						 attribute:NSLayoutAttributeNotAnAttribute
                            						multiplier:1.0
                              						  constant:10]];
[someView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[view1][view2][view3]|"
                                        						 options:(NSLayoutFormatAlignAllLeft | 
                                                 						  NSLayoutFormatAlignAllRight)
                                        						 metrics:nil
                                          						   views:NSDictionaryOfVariableBindings(view1, view2, view3)]];
[someView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[view1]|"
                                        						 options:NSLayoutFormatDirectionLeadingToTrailing
                                        						 metrics:nil
                                          						   views:NSDictionaryOfVariableBindings(view1)]];

[someView addConstraints:PVGroup(@[PVLeftOf(view).equalTo.constant(10),
								   PVVFL(@"V:|[view1][view2][view3]|").alignAllLeftAndRight,
								   PVVFL(@"H:|[view1]|")
								   ]).withViews(NSDictionaryOfVariableBindings(view1, view2, view3)).asArray];

You can also use usual NSLayoutConstraint or NSArray of NSLayoutConstraint as an item for PVGroup(). Following code is totally acceptable:

NSLayoutConstraint* usualConstraint = [NSLayoutConstraint constraintWithItem:... blablabla very long constraint definition ...];
NSArray* usualConstraints = [NSLayoutConstraint constraintsWithVisualFormat:... blabla ...];

[someView addConstraints:PVGroup(@[usualConstraint, usualConstraints]).asArray];

Alternatives

• Masonry
• NSLayoutEquations
• KeepLayout
• FLKAutoLayout

Installation

Use cocoapods!

pod 'Parus'

#import <Parus/Parus.h>

TODO

• Mac OS X support;
• Extend debug description;
• Category for NSString as a start point for creating VFL.

More information

Visit our wiki