Label 自適應文本(StoryBoard/xib)

To make your label automatically resize height you need to do following:

1. Set layout constrains for label
2. Set height constraint with low priority. It should be lower than ContentCompressionResistancePriority
3. Set numberOfLines = 0
4. Set ContentHuggingPriority higher than label's height priority
5. Set preferredMaxLayoutWidth for label. That value is used by label to calculate its height

For example:

self.descriptionLabel = [[UILabel alloc] init];
self.descriptionLabel.numberOfLines = 0;
self.descriptionLabel.lineBreakMode = NSLineBreakByWordWrapping;
self.descriptionLabel.preferredMaxLayoutWidth = 200;

[self.descriptionLabel setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[self.descriptionLabel setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[self.descriptionLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self addSubview:self.descriptionLabel];

NSArray* constrs = [NSLayoutConstraint constraintsWithVisualFormat:@"|-8-[descriptionLabel_]-8-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(descriptionLabel_)];
[self addConstraints:constrs];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-8-[descriptionLabel_]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(descriptionLabel_)]];
[self.descriptionLabel addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[descriptionLabel_(220@300)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(descriptionLabel_)]];

Using Interface Builder

1. Set up four constraints. The height constraint is mandatory.

2. Then go to the label's attributes inspector and set number of lines to 0.

3. Go to the label's size inspector and increase vertical ContentHuggingPriority and vertical ContentCompressionResistancePriority.
   

4. Select and edit height constraint.
   

5. And decrease height constraint priority.
   

Enjoy. :)