Indicates the lowest vertical extent for your onscreen content, for use with Auto Layout constraints.
- iOS 7.0–11.0Deprecated
- tvOS 9.0–11.0Deprecated
bottom property comes into play when a view controller is frontmost onscreen. It indicates the lowest vertical extent for content that you don't want to appear behind a translucent or transparent UIKit bar (such as a tab bar or toolbar). This property implements the
UILayout protocol and you can employ it as a constraint item when using the
The value of this property is, specifically, the value of the
length property of the object returned when you query this property. This value is constrained by either the view controller or by its enclosing container view controller (such as a navigation or tab bar controller), as follows:
A view controller not within a container view controller constrains this property to indicate the top of the tab bar or toolbar, if one of these is visible, or else to indicate the bottom edge of the view controller's view.
A view controller within a container view controller does not set this property’s value. Instead, the container view controller constrains the value to indicate the top of the tab bar or toolbar, if one of these is visible, or else to indicate the bottom edge of the view controller's view.
If a container view controller's toolbar or tab bar is visible and opaque, the container lays out the frontmost view controller's view so its bottom edge abuts the top of the bar. In this case, the value of this property is 0.
Query this property within your implementation of the
When laying out a storyboard scene, the Bottom Layout Guide object is available in the Interface Builder outline view as a child of the View Controller object. Adding a bottom layout guide using Interface Builder provides backward layout compatibility to iOS 6.
As an example of how to programmatically use this property with Auto Layout, say you want to position a control such that its bottom edge is 20 points above the bottom layout guide. This scenario applies to any of the scenarios listed above. Use code similar to the following:
To use a bottom layout guide without using constraints, obtain the guide’s position relative to the bottom bound of the containing view. In the case of using a view controller subclass, obtain the numbers you need as follows:
In the case of using a view subclass, obtain the numbers you need as follows: