title: Swift 4.0 cannot invoke initializer for type 'NSLayoutConstraint' with an argument list of type '(NSLayoutConstraint)'
body: <p>I am using XCode Version 9.0 (9A235), macOS Sierra Version 10.12.6 (16G29),  iOS 11.0.</p>
  
  <p>I need to add constraint into array and then later I need to activate it.</p>
  
  <p>For doing this I did like...</p>
  
  <pre><code>// 1.Declare and initialized  the constraint
  
  private lazy var labelConstraints = [NSLayoutConstraint]()
  
  // 2.Prepare constraint   
  let widthConstraint = 
      headerLabel.widthAnchor.constraint(equalTo: licenseLabel.widthAnchor)
  
  // 3.Constraint added into the array   
  labelConstraints.append(NSLayoutConstraint(widthConstraint))
  
  // 4.Finally activate the constraints   
  labelConstraints.activate()
  </code></pre>
  
  <p>After build my xcode project it throws an error like  </p>
  
  <pre><code>ERROR: **cannot invoke initializer for type 'NSLayoutConstraint' with an argument list of type '(NSLayoutConstraint)'** 
  
  **labelConstraints.append(NSLayoutConstraint(widthConstraint))**
  </code></pre>