'Constant不是有限的！这是非法的。constant:nan‘目标C中的错误

Question

当我尝试启动我正在处理的应用程序时，我收到以下错误。“常量不是有限的！这是非法的。常量:南”

这是一个学校项目的instagram的克隆。我认为错误在子视图中，或者可能是在创建的约束中，但不幸的是，我就是看不到问题。

- (void) layoutSubviews {
    [super layoutSubviews];

     // Before layout, calculate the intrinsic size of the labels (the size they "want" to be), and add 20 to the height for some vertical padding.
    CGSize maxSize = CGSizeMake(CGRectGetWidth(self.bounds), CGFLOAT_MAX);
    CGSize usernameLabelSize = [self.usernameAndCaptionLabel sizeThatFits:maxSize];
    CGSize commentLabelSize = [self.commentLabel sizeThatFits:maxSize];

    self.usernameAndCaptionLabelHeightConstraint.constant = usernameLabelSize.height + 20;
    self.commentLabelHeightConstraint.constant = commentLabelSize.height + 20;
    self.imageHeightConstraint.constant = self.mediaItem.image.size.height / self.mediaItem.image.size.width * CGRectGetWidth(self.contentView.bounds);

    // Hide the line between cells
    self.separatorInset = UIEdgeInsetsMake(0, 0, 0, CGRectGetWidth(self.bounds));
}

NSDictionary *viewDictionary = NSDictionaryOfVariableBindings(_mediaImageView, _usernameAndCaptionLabel, _commentLabel);

    [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_mediaImageView]|" options:kNilOptions metrics:nil views:viewDictionary]];
    [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_usernameAndCaptionLabel]|" options:kNilOptions metrics:nil views:viewDictionary]];
    [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_commentLabel]|" options:kNilOptions metrics:nil views:viewDictionary]];

    [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[_mediaImageView][_usernameAndCaptionLabel][_commentLabel]" options:kNilOptions metrics:nil views:viewDictionary]];



    self.imageHeightConstraint = [NSLayoutConstraint constraintWithItem:_mediaImageView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:100];
    self.imageHeightConstraint.identifier = @"Image height constraint";

    self.usernameAndCaptionLabelHeightConstraint = [NSLayoutConstraint constraintWithItem:_usernameAndCaptionLabel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:100];
    self.usernameAndCaptionLabelHeightConstraint.identifier = @"Username and caption label height constraint";

    self.commentLabelHeightConstraint = [NSLayoutConstraint constraintWithItem:_commentLabel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:100];
    self.commentLabelHeightConstraint.identifier = @"Comment label height constraint";

    [self.contentView addConstraints:@[self.imageHeightConstraint, self.usernameAndCaptionLabelHeightConstraint, self.commentLabelHeightConstraint]];


}

Answer 1

我只看到一个地方你在做除法：

self.imageHeightConstraint.constant = self.mediaItem.image.size.height / self.mediaItem.image.size.width * CGRectGetWidth(self.contentView.bounds);

在此行上设置一个断点，看看self.mediaItem.image.size是什么样子。