NSLayoutConstraint : resize view when needed - cocoa

Question

I have 2 "sister view" located one above the other (talking Y) embedded in the same parent view.
The first one is the size of the screen et the one below is outside of the screen at the bottom.
On a animation, the bottom view raises and shows up on the screen.
This animation should reduce the height of the upper view.
I thought using NSLayoutConstraint for this but I can't get work.
Right now I have following :
let constraintString : String = String(format: "V:[tranlucentView][buttonContainer(%lg)]", buttonHeight * countOfButtons)
let viewsDict:NSDictionary = ["tranlucentView" : self.translucentView, "buttonContainer" : self.buttonContainer]
var constraints : NSArray = NSLayoutConstraint.constraintsWithVisualFormat(constraintString, options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict)
self.view.addConstraints(constraints)
And that's the error I'm getting :
Probably at least one of the constraints in the following list is one you don't want. Try
this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x198f6530 V:[UIView:0x198ef880]-(0)-[UIView:0x177b11e0]>",
"<NSLayoutConstraint:0x198f6600 V:[UIView:0x177b11e0(0)]>",
"<NSAutoresizingMaskLayoutConstraint:0x19f7f7f0 h=--& v=--& UIView:0x198ef880.midY == + 284>",
"<NSAutoresizingMaskLayoutConstraint:0x1983e4c0 h=--& v=--& V:[UIView:0x198ef880(568)]>",
"<NSAutoresizingMaskLayoutConstraint:0x19f7f260 h=--& v=--& UIView:0x177b11e0.midY == + 472>"
)
Any suggestions for my problem ?

Answer 1

I found the solution myself :
I needed to translatesAutoresizingMaskIntoConstraints to false for my upper-view to allow its resize.
Also I needed to add a constraint for its width or else its width goes to 0.
let constraintString : String = String(format: "V:|[tranlucentView][buttonContainer(%lg)]|", buttonHeight * countOfButtons)
self.translucentView.setTranslatesAutoresizingMaskIntoConstraints(false)
let viewsDict:NSDictionary = ["tranlucentView" : self.translucentView, "buttonContainer" : self.buttonContainer]
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(constraintString, options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[tranlucentView]|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))