# constraint(equalTo:) Returns a constraint that defines one item’s attribute as equal to another. ``` func constraint(equalTo anchor: NSLayoutAnchor) -> NSLayoutConstraint ``` ## Parameters `anchor` A layout anchor from a [`UIView`](/documentation/UIKit/UIView), , or [`UILayoutGuide`](/documentation/UIKit/UILayoutGuide) object. You must use a subclass of [`NSLayoutAnchor`](/documentation/UIKit/NSLayoutAnchor) that matches the current anchor. For example, if you call this method on an [`NSLayoutXAxisAnchor`](/documentation/UIKit/NSLayoutXAxisAnchor) object, this parameter must be another [`NSLayoutXAxisAnchor`](/documentation/UIKit/NSLayoutXAxisAnchor). ## Return Value An [`NSLayoutConstraint`](/documentation/UIKit/NSLayoutConstraint) object that defines an equal relationship between the attributes represented by the two layout anchors. ## Discussion This method defines the relationship `first attribute = second attribute`. Where `first attribute` is the layout attribute represented by the anchor receiving this method call, and `second attribute` is the layout attribute represented by the `anchor` parameter. The constraints produced by the following two examples are identical. ```objc // Creating a constraint using NSLayoutConstraint [NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeadingMargin multiplier:1.0 constant:0.0].active = YES; // Creating the same constraint using constraintEqualToAnchor: UILayoutGuide *margin = self.view.layoutMarginsGuide; [subview.leadingAnchor constraintEqualToAnchor:margin.leadingAnchor].active = YES; ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)