handy categories for generate NSLayoutConstraint programatically.
[self.view addConstraint:[self.tableView constraintCenterXEqualToView:self.view]];
[self.view addConstraint:[self.tableView constraintWidthEqualToView:self.view]];
[self.view addConstraints:[self.nextStepButton constraintsSize:CGSizeMake(300.0f, 40.0f)]];
[self.view addConstraint:[self.nextStepButton constraintCenterXEqualToView:self.view]];