Programmatically layout multiple views using constraints

Question

How do I create a 2 x 2 grid of UIViews programmatically using constraints in objective-c?

For example, I have four UIViews with their names corresponding to their row/column position (oneOne, oneTwo, twoOne, twoTwo) as per the below image.

Here is the code I am currently using:

-(void)buildGrid {

    [self.view setTranslatesAutoresizingMaskIntoConstraints:NO];
   
    UIView *oneOne = [UIView new];
    [oneOne setBackgroundColor:[UIColor redColor]];
    [oneOne setTranslatesAutoresizingMaskIntoConstraints:NO];

    UIView *oneTwo = [UIView new];
    [oneTwo setBackgroundColor:[UIColor greenColor]];
    [oneTwo setTranslatesAutoresizingMaskIntoConstraints:NO];

    UIView *twoOne = [UIView new];
    [twoOne setBackgroundColor:[UIColor blueColor]];
    [twoOne setTranslatesAutoresizingMaskIntoConstraints:NO];

    UIView *twoTwo = [UIView new];
    [twoTwo setBackgroundColor:[UIColor purpleColor]];
    [twoTwo setTranslatesAutoresizingMaskIntoConstraints:NO];

    [self.view addSubview:oneOne];
    [self.view addSubview:oneTwo];
    [self.view addSubview:twoOne];
    [self.view addSubview:twoTwo];

    NSDictionary *viewsDict = NSDictionaryOfVariableBindings(oneOne, oneTwo, twoOne, twoTwo);



    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[oneOne]-10-[twoOne]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:viewsDict]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[oneOne]-10-[twoOne]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:viewsDict]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[oneTwo]-10-[twoTwo]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:viewsDict]];


    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[twoOne]-10-[twoTwo]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:viewsDict]];

}

I have followed several tutorials but none (so far) have described how to create this kind of 'grid' layout, they have been far simpler like a single 'column' of UIViews but when I had further 'columns' I get errors about not being able to maintain the constraints:

Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.

This code works fine if I make it four UIViews going down or accross the screen but not if I make it 2 x 2. What am I doing wrong?

Update

As per accepted answer the constraints should have been:

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[oneOne]-10-[twoOne(==oneOne)]-10-|"
                                                                  options:0
                                                                  metrics:nil
                                                                    views:viewsDict]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[oneTwo]-10-[twoTwo(==oneTwo)]-10-|"
                                                                  options:0
                                                                  metrics:nil
                                                                    views:viewsDict]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[oneOne]-10-[oneTwo(==oneOne)]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:viewsDict]];


    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[twoOne]-10-[twoTwo(==twoOne)]-10-|"
                                                                  options:0
                                                                  metrics:nil
                                                                    views:viewsDict]];

Do you need to use Visual Format? I'd suggest using some kind of layouting library like Masonry or KeepLayout - it will be easier to create complex layouts from code with them. — Losiowaty
– Losiowaty, Commented Nov 10, 2015 at 9:21
In all constraints set options to 0 instead of NSLayoutFormatDirectionLeadingToTrailing and see if you get the desired result — harsha yarabarla
– harsha yarabarla, Commented Nov 10, 2015 at 9:24
I have never heard of these libraries, I'll take a look now. I was kind of hoping this layout would be fairly simple and not uncommon. — Agamemnon
– Agamemnon, Commented Nov 10, 2015 at 9:25
@harshayarabarla - Just tired options:0 and no difference, unfortunately. — Agamemnon
– Agamemnon, Commented Nov 10, 2015 at 9:26
1) V:|-10-[oneOne]-10-[twoOne]-10-| 2) H:|-10-[oneOne]-10-[oneTwo]-10-| 3) V:|-10-[oneTwo]-10-[twoTwo]-10-| 4) H:|-10-[twoOne]-10-[twoTwo]-10-| keep these 4 constraints as it is and give options 0 for all of them..... i see in your second constraint you set horizontal constraint with vertical views — harsha yarabarla
– harsha yarabarla, Commented Nov 10, 2015 at 9:29

psci · Accepted Answer · 2015-11-10 09:28:29Z

1

First of you have error in second constraint. It should be:

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[oneOne]-10-[oneTwo]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:viewsDict]];

Also your layout still doesn't contain any information about subviews size (width and height). You have to add constraints like this (in pseudocode)

 oneOne.width = oneTwo.width = twoOne.width = twoTwo.width
 oneOne.height = oneTwo.height = twoOne.height = twoTwo.height

answered Nov 10, 2015 at 9:28

psci

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2 Comments

Agamemnon Over a year ago

This problem was caused by a combination of not setting the widths to anything and the correction of the second constraint as you highlighted. I have set the widths in the constraints themselves: "V:|-10-[oneOne]-10-[twoOne(==oneOne)]-10-|". Thanks.

psci Over a year ago

Didn't even know about [twoOne(==oneOne)] trick, so also thank you :)

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