在autolayout中加入每个view的weight

在autolayout中加入每个view的weight，这样相互之间的关系就更明确，比如：

　　double iconViewWeight = 1;

    double titleLabelWeight = 12;

    double timeLabelWeight = 3;

    

    double standardWeigth = iconViewWeight;

    double iconViewWeightRatio = iconViewWeight / standardWeigth;

    double titileLabelWightRatio = titleLabelWeight / standardWeigth;

    double timeLabelWightRatio = timeLabelWeight / standardWeigth;

    

    UIView *standardView = _iconView;

    

    NSDictionary *views = NSDictionaryOfVariableBindings(_iconView, _titileLabel, _timeLabel, bgImageView);

    NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:_iconView

                                                                  attribute:NSLayoutAttributeWidth

                                                                  relatedBy:NSLayoutRelationEqual

                                                                     toItem:standardView

                                                                  attribute:NSLayoutAttributeWidth

                                                                 multiplier:iconViewWeightRatio

                                                                   constant:0.0f];

    [self addConstraint:constraint];

    

    constraint = [NSLayoutConstraint constraintWithItem:_titileLabel

                                              attribute:NSLayoutAttributeWidth

                                              relatedBy:NSLayoutRelationEqual

                                                 toItem:standardView

                                              attribute:NSLayoutAttributeWidth

                                             multiplier:titileLabelWightRatio

                                               constant:0.0f];

    [self addConstraint:constraint];

    constraint = [NSLayoutConstraint constraintWithItem:_timeLabel

                                              attribute:NSLayoutAttributeWidth

                                              relatedBy:NSLayoutRelationEqual

                                                 toItem:standardView

                                              attribute:NSLayoutAttributeWidth

                                             multiplier:timeLabelWightRatio

                                               constant:0.0f];

    [self addConstraint:constraint];

    

    constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-[_iconView]-[_titileLabel]-[_timeLabel]-|"

                                                          options:NSLayoutFormatAlignAllCenterY

                                                          metrics:nil

                                                            views:views];

    [self addConstraints:constraints];



    constraint = [NSLayoutConstraint constraintWithItem:_iconView

                                              attribute:NSLayoutAttributeCenterY

                                              relatedBy:NSLayoutRelationEqual

                                                 toItem:self.contentView

                                              attribute:NSLayoutAttributeCenterY

                                             multiplier:1.0

                                               constant:0.0f];

    [self addConstraint:constraint];

代码更加简介，但这适用于一些特定的场合