NSLayoutConstraint in a Loop FOR - ios

Question

I'm trying to create UILabel through a for loop that gets its NSInteger from an NSArray. The cycle works properly but I can not see all the vertices one below the other. I'm definitely wrong something with constraint. Can you help me?
Based on this code I posted how can I fix the NSLayoutConstraint problem within a for loop?
NSInteger max = [[_yValueArray valueForKeyPath:#"#max.self"] integerValue];
NSInteger min = [[_yValueArray valueForKeyPath:#"#min.self"] integerValue];
for (NSInteger value = max; value >= min; value -=1) {
UILabel *valueLabel = [[UILabel alloc] init];
valueLabel.textColor = [UIColor lightGrayColor];
valueLabel.backgroundColor = [UIColor redColor];
valueLabel.textAlignment = NSTextAlignmentLeft;
valueLabel.font = [UIFont defaultAppFontWithSize:10];
valueLabel.translatesAutoresizingMaskIntoConstraints = NO;
valueLabel.text = [self yValueString:value];
valueLabel.tag = value;
[yAxisView addSubview:valueLabel];
[yAxisView addConstraint:[NSLayoutConstraint constraintWithItem:valueLabel attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:valueLine attribute:NSLayoutAttributeLeft multiplier:1 constant:-2]];
NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:valueLabel attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:yAxisView attribute:NSLayoutAttributeTop multiplier:1 constant:0];
[yAxisView addConstraint:topConstraint];
NSLayoutConstraint *height = [NSLayoutConstraint constraintWithItem:valueLabel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:valueLine attribute:NSLayoutAttributeHeight multiplier:1 constant:10];
[yAxisView addConstraint: height];
// topConstraint.constant += height.constant;
}
What I'm trying to get is a bar graph like this ... At this time I wanted to get the result of the Y axis you see in the image ...

Answer 1

I'm gathering that the question is labeling the left axis vertically.
If your goal is to add labels to the left edge, you can set the centerY constraint as a multiple of the centerY of its superview. The only trick is that it doesn't like a 0 for the multiplier for centerY, so for that top one, I'd just set the centerY to be equal to the top of its superview. Thus:
NSInteger max = 10;
for (NSInteger i = 0; i <= max; i++) {
UILabel *label = [[UILabel alloc] init];
label.translatesAutoresizingMaskIntoConstraints = false;
label.text = [NSString stringWithFormat:#"%ld", (long)i];
[self.chartDataView addSubview:label];
CGFloat multiplier = (CGFloat)(max - i) * 2.0 / (CGFloat)max;
[self.chartDataView addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:self.chartDataView attribute:NSLayoutAttributeLeft multiplier:1 constant:-5]];
if (multiplier == 0) {
[self.chartDataView addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.chartDataView attribute:NSLayoutAttributeTop multiplier:1 constant:0]];
} else {
[self.chartDataView addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.chartDataView attribute:NSLayoutAttributeCenterY multiplier:multiplier constant:0]];
}
}
Yields:
Clearly, I'm not drawing any chart, but this shows how, given a chart graph area, you can use the multiplier to dictate where the labels go.