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# NSLayoutConstraint.Attribute

The part of the object’s visual representation that should be used to get the value for the constraint.

```
enum Attribute
```

## Topics

### Constants

[`NSLayoutConstraint.Attribute.left`](/documentation/UIKit/NSLayoutConstraint/Attribute/left)

The left side of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.right`](/documentation/UIKit/NSLayoutConstraint/Attribute/right)

The right side of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.top`](/documentation/UIKit/NSLayoutConstraint/Attribute/top)

The top of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.bottom`](/documentation/UIKit/NSLayoutConstraint/Attribute/bottom)

The bottom of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.leading`](/documentation/UIKit/NSLayoutConstraint/Attribute/leading)

The leading edge of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.trailing`](/documentation/UIKit/NSLayoutConstraint/Attribute/trailing)

The trailing edge of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.width`](/documentation/UIKit/NSLayoutConstraint/Attribute/width)

The width of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.height`](/documentation/UIKit/NSLayoutConstraint/Attribute/height)

The height of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.centerX`](/documentation/UIKit/NSLayoutConstraint/Attribute/centerX)

The center along the x-axis of the object’s alignment rectangle.

[`NSLayoutConstraint.Attribute.centerY`](/documentation/UIKit/NSLayoutConstraint/Attribute/centerY)

The center along the y-axis of the object’s alignment rectangle.

[`NSLayoutAttributeBaseline`](/documentation/UIKit/NSLayoutAttribute/NSLayoutAttributeBaseline)

The object’s baseline.

[`NSLayoutConstraint.Attribute.lastBaseline`](/documentation/UIKit/NSLayoutConstraint/Attribute/lastBaseline)

The object’s baseline.

[`NSLayoutConstraint.Attribute.firstBaseline`](/documentation/UIKit/NSLayoutConstraint/Attribute/firstBaseline)

The object’s baseline.

[`NSLayoutConstraint.Attribute.leftMargin`](/documentation/UIKit/NSLayoutConstraint/Attribute/leftMargin)

The object’s left margin.

[`NSLayoutConstraint.Attribute.rightMargin`](/documentation/UIKit/NSLayoutConstraint/Attribute/rightMargin)

The object’s right margin.

[`NSLayoutConstraint.Attribute.topMargin`](/documentation/UIKit/NSLayoutConstraint/Attribute/topMargin)

The object’s top margin.

[`NSLayoutConstraint.Attribute.bottomMargin`](/documentation/UIKit/NSLayoutConstraint/Attribute/bottomMargin)

The object’s bottom margin.

[`NSLayoutConstraint.Attribute.leadingMargin`](/documentation/UIKit/NSLayoutConstraint/Attribute/leadingMargin)

The object’s leading margin.

[`NSLayoutConstraint.Attribute.trailingMargin`](/documentation/UIKit/NSLayoutConstraint/Attribute/trailingMargin)

The object’s trailing margin.

[`NSLayoutConstraint.Attribute.centerXWithinMargins`](/documentation/UIKit/NSLayoutConstraint/Attribute/centerXWithinMargins)

The center along the x-axis between the object’s left and right margin.

[`NSLayoutConstraint.Attribute.centerYWithinMargins`](/documentation/UIKit/NSLayoutConstraint/Attribute/centerYWithinMargins)

The center along the y-axis between the object’s top and bottom margin.

[`NSLayoutConstraint.Attribute.notAnAttribute`](/documentation/UIKit/NSLayoutConstraint/Attribute/notAnAttribute)

A placeholder value for indicating that the constraint’s second item and second attribute aren’t used in any calculations.


---

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