Objective C: Center with NSLayoutConstraint - ios

Question

NSArray *imageViewHorConst2 = [NSLayoutConstraint constraintsWithVisualFormat:#"H:[_startbutton(50)]-30-[_resetbutton(50)]" options:0 metrics:nil views:viewsDictionary2];}
I'm trying to get those 2 buttons (startbutton, resetbutton) to be separated by some value and be centred.
I'm not sure how to do this in objective C

Answer 1

Here is the snippet to add the two buttons in the center of the screen separated by 30 pixels:
UIButton *button1 = [[UIButton alloc] init];
button1.translatesAutoresizingMaskIntoConstraints = FALSE;
[button1 setTitle:#"Button 1" forState:UIControlStateNormal];
button1.backgroundColor = [UIColor blueColor];
UIButton *button2 = [[UIButton alloc] init];
button2.translatesAutoresizingMaskIntoConstraints = FALSE;
[button2 setTitle:#"Button 2" forState:UIControlStateNormal];
button2.backgroundColor = [UIColor brownColor];
// Add a container view to hold two buttons
UIView *containerView = [[UIView alloc] init];
containerView.translatesAutoresizingMaskIntoConstraints = FALSE;
[containerView addSubview:button1];
[containerView addSubview:button2];
// vertical constraints
[containerView addConstraints: [NSLayoutConstraint constraintsWithVisualFormat:#"V:|[button1]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(button1)]];
[containerView addConstraints: [NSLayoutConstraint constraintsWithVisualFormat:#"V:|[button2]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(button2)]];
// horizontal constraints
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[button1]-(30)-[button2]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(button1, button2)]];
// Add the container view with centerx and centery constraints to
// keep the buttons in the center
[self.view addSubview:containerView];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0]];
Screenshot:

Answer 2

You can easily accomplish this with UIStackView
self.view.backgroundColor = [UIColor redColor];
UIStackView*st = [UIStackView new];
st.distribution = UIStackViewDistributionFillEqually;
st.axis = UILayoutConstraintAxisHorizontal;
st.spacing = 40;
UIButton*b1 = [UIButton buttonWithType:UIButtonTypeSystem];
UIButton*b2 = [UIButton buttonWithType:UIButtonTypeSystem];
[b1 setTitle:#"ClickB1" forState:UIControlStateNormal];
[b2 setTitle:#"ClickB2" forState:UIControlStateNormal];
st.translatesAutoresizingMaskIntoConstraints = NO;
b1.translatesAutoresizingMaskIntoConstraints = NO;
b2.translatesAutoresizingMaskIntoConstraints = NO;
[st addArrangedSubview:b1];
[st addArrangedSubview:b2];
[self.view addSubview:st];
[[st.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor] setActive:YES];
[[st.centerYAnchor constraintEqualToAnchor:self.view.centerYAnchor] setActive:YES];