On iPhone and iPad if one's designs were reasonably complex, you would have to be involved in writing a lot of code to support such adaptive layouts. With Auto Layout it makes it easy to support different screen sizes in your apps.

1. Auto-Layout
in iOS 7
By Pushpendra Singh

2. Layout
Layout Consist of four things:
• Center
• Bounds
• Auto-resizing mask
• Transform

3. Auto Layout
Using Auto Layout, you can create a
dynamic and versatile interface that
responds appropriately to changes in
screen size, device orientation, and
localization.

4. Basic Concept
Expression of the form y = m*x + b,
where:
y and x are attributes of views.
m and b are floating point values.
An attribute is one of left, right, top,
bottom, leading, trailing, width, height,
centerX, centerY, and baseline.

5. constraints
Layout NSLayoutConstraint
Content NSContentSizeLayoutConstraint
AutosizingNSAutoresizingMaskLayoutConstraint

6. Constraints Attribute
view1.attribute1 RELATION multiplier * view2.attribute2 +
constant
NSLayoutAttributeLeft
NSLayoutAttributeRight
NSLayoutAttributeTop
NSLayoutAttributeBottom
NSLayoutAttributeLeading
NSLayoutAttributeTrailing
NSLayoutAttributeWidth
NSLayoutAttributeHeight
NSLayoutAttributeCenterX
NSLayoutAttributeCenterY
NSLayoutAttributeBaseline
NSLayoutRelationEqual
NSLayoutRelationGreaterThanOrEqual
NSLayoutRelationLessThanOrEqual
NSLayoutAttributeNotAnAttribute

8. Constraints Code
view1.attribute1 RELATION multiplier * view2.attribute2 +
constant
constraint = [NSLayoutConstraint
constraintWithItem: view
attribute: NSLayoutAttributeWidth
relatedBy: NSLayoutRelationEqual
toItem: nil
attribute: NSLayoutAttributeNotAnAttribute
multiplier: 1.0
constant:100.0];
[view addConstraint: constraint];
constraint = [NSLayoutConstraint
constraintWithItem: view
attribute: NSLayoutAttributeWidth
relatedBy: NSLayoutRelationEqual
toItem: nil
attribute: NSLayoutAttributeNotAnAttribute
multiplier: 1.0
Constant: 80.0];
[view addConstraint: constraint];

9. Check For Ambiguous Layout
view.hasAmbiguousLayout
view.exerciseAmbiguityInLayout
for (UIView *view in self.subviews) {
if ([view hasAmbiguousLayout]){
NSLog(@"<%@:0x%0x>", view.description, (int)self);
}
}

10. Intrinsic ContentSize
Suggested size for the view.
- (CGSize) intrinsicContentSize {
return mySize;
}
[self invalidateIntrinsicContentSize];
UIImage *img = UIImage imageNamed:@"Icon.png"];
UIImageView *iv = [[UIImageView alloc] initWithImage:img];
NSLog(@"%@", NSStringFromCGSize(iv.intrinsicContentSize));

11. Visual Format Language
[NSLayoutConstraint
! constraintsWithVisualFormat:@"H:|-[buttonA]-|" ! options:0
! metrics:nil
! views:@{@"buttonA":buttonA}];

12. UIView
Opting in to Constraint-Based Layout
+ requiresConstraintBasedLayout
– translatesAutoresizingMaskIntoConstraints
– setTranslatesAutoresizingMaskIntoConstraints:
Managing Constraints
–
–
–
–
–
constraints
addConstraint:
addConstraints:
removeConstraint:
removeConstraints:
Measuring in Constraint-Based Layout
–
–
–
–
–
–
–
systemLayoutSizeFittingSize
intrinsicContentSize
invalidateIntrinsicContentSize
contentCompressionResistancePriorityForAxis:
setContentCompressionResistancePriority:forAxis:
contentHuggingPriorityForAxis:
setContentHuggingPriority:forAxis:

13. UIView
Aligning Views with Constraint-Based Layout
–
–
–
–
alignmentRectForFrame:
frameForAlignmentRect:
alignmentRectInsets
viewForBaselineLayout
Triggering Constraint-Based Layout
–
–
–
–
needsUpdateConstraints
setNeedsUpdateConstraints
updateConstraints
updateConstraintsIfNeeded
Debugging Constraint-Based Layout
– constraintsAffectingLayoutForAxis:
– hasAmbiguousLayout
– exerciseAmbiguityInLayout

14. Queries