Question

我开始欣赏Auto Layout为我所做的工作，但我与布伦特西蒙斯就not using Interface Builder的主题建立了约束。 Apple提供的界面非常灵活，但极其冗长 - 明确设计用于代码生成器而非人类使用。对我而言，它例证了最糟糕的Objective-C，重复了过长的相同前缀，很少使用参数来模糊所有含义，而不是为代码提供清晰度。我见过Florian Kugler's FLKAutoLayout隐藏了UIView中类别中的约束创建。

还有其他方法可以使代码中的布局约束更清晰，更容易理解吗？

Answer 1

Jonas Budelmann的

Masonry是一个用于自动布局的DSL，它比手动创建的线条和布局约束更易读。通过iOS Dev Weekly。

UIEdgeInsets padding = UIEdgeInsetsMake(10, 10, 10, 10);

[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.equalTo(superview.mas_top).with.offset(padding.top);
    make.left.equalTo(superview.mas_left).with.offset(padding.left);
    make.bottom.equalTo(superview.mas_bottom).with.offset(-padding.bottom);
    make.right.equalTo(superview.mas_right).with.offset(-padding.right);
}];

它还具有设置边，大小和中心的复合约束：

// make top, left, bottom, right equal view2
make.edges.equalTo(view2);

// make top = superview.top + 5, left = superview.left + 10,
//      bottom = superview.bottom - 15, right = superview.right - 20
make.edges.equalTo(superview).insets(UIEdgeInsetsMake(5, 10, 15, 20))

// make width and height greater than or equal to titleLabel
make.size.greaterThanOrEqualTo(titleLabel) 

// make width = superview.width + 100, height = superview.height - 50
make.size.equalTo(superview).sizeOffset(CGSizeMake(100, -50))

// make centerX and centerY = button1
make.center.equalTo(button1) 

// make centerX = superview.centerX - 5, centerY = superview.centerY + 10
make.center.equalTo(superview).centerOffset(CGPointMake(-5, 10))

Answer 2

我尽量保持与Apple的实施尽可能接近，承认存在NSLayoutConstraint，所以我只是定义了一组 Concise Auto Layout macros 从属性和关系中删除前缀，并将约束创建包装在类似构造函数的宏中（也省略了我从未使用过的乘数参数）：

Constraint
ConstantConstraint
VisualConstraints
VisualConstraintWithMetrics

要将多个简单约束附加到视图中，我将它们包装在数组文字中。我总是在非零常数前面加上一个符号，以强调位移。在实践中，它看起来像这样（实例变量对视图有影响）：

[self.view addConstraints:
 @[Constraint(_verticalSeparator, CenterX, Equal, _top, CenterX, 0),
 Constraint(_verticalSeparator, CenterY, Equal, _top, CenterY, +22),
 Constraint(_verticalSeparator, Height, Equal, _localWeather, Height, 0),
 Constraint(_localWeather, CenterY, Equal, _verticalSeparator, CenterY, 0),
 Constraint(_addLocation, CenterY, Equal, _verticalSeparator, CenterY, 0),
 Constraint(_touchDown, Trailing, Equal, _verticalSeparator, Trailing, -1),
 Constraint(_touchDown, CenterY, Equal, _localWeather, CenterY, 0),
 Constraint(_touchDown, Width, Equal, _localWeather, Width, +26),
 Constraint(_touchDown, Height, Equal, _localWeather, Height, 0)
]];

id f = @"[_localWeather]-space-[_verticalSeparator]-space-[_addLocation]";
[self.view addConstraints:
 VisualConstraintWithMetrics(f, @{@"space": @11},
                             _localWeather, _verticalSeparator, _addLocation)];


[_tableCell addConstraint:ConstantConstraint(_tableCell, Height, Equal, 44)];

当处理所有共享相同设置的视图组时，我会像这样枚举数组文字：

[@[_top, _middle, _bottom, _touchDown, _verticalSeparator]
 enumerateObjectsUsingBlock:^(UIView *view, NSUInteger idx, BOOL *stop) {
    view.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:view];
}];

水平地填充superview经常发生，它被提升到自己的宏：

[@[_top, _middle, _bottom] enumerateObjectsUsingBlock:horizontallyFillSuperview];

随着我的风格发展，我会更新这个答案......

Answer 3

您也可以使用Parus lib来指定约束。这个lib的主要思想是不与NSLayoutConstraint本身分开，并允许你根据需要使用约束进行操作。

例如：

[self.view addConstraints:
@[Constraint(_verticalSeparator, CenterX, Equal, _top, CenterX, 0),
  Constraint(_verticalSeparator, CenterY, Equal, _top, CenterY, +22),
  Constraint(_verticalSeparator, Height, Equal, _localWeather, Height, 0),
  Constraint(_localWeather, CenterY, Equal, _verticalSeparator, CenterY, 0),
  Constraint(_addLocation, CenterY, Equal, _verticalSeparator, CenterY, 0),
  Constraint(_touchDown, Trailing, Equal, _verticalSeparator, Trailing, -1),
  Constraint(_touchDown, CenterY, Equal, _localWeather, CenterY, 0),
  Constraint(_touchDown, Width, Equal, _localWeather, Width, +26),
  Constraint(_touchDown, Height, Equal, _localWeather, Height, 0)
]];

id f = @"[_localWeather]-space-[_verticalSeparator]-space-[_addLocation]";
[self.view addConstraints:
VisualConstraintWithMetrics(f, @{@"space": @11},
                         _localWeather, _verticalSeparator, _addLocation)];

看起来像：

[self.view addConstraints PVGroup(@[
  PVCenterXOf(_verticalSeparator).equalTo.centerXOf(_top),
  PVCenterYOf(_verticalSeparator).equalTo.centerYOf(_top).plus(22),
  PVHeightOf(_verticalSeparator).equalTo.heightOf(_localWeather),
  PVCenterYOf(_localWeather).equalTo.centerYOf(_verticalSeparator),
  PVCenterYOf(_addLocation).equalTo.centerYOf(_verticalSeparator),
  PVTrailingOf(_touchDown).equalTo.trailingOf(_verticalSeparator).minus(1),
  PVCenterYOf(_touchDown).equalTo.centerYOf(_localWeather),
  PVWidthOf(_touchDown).equalTo.widthOf(_localWeather).plus(26),
  PVHightOf(_touchDown).equalTo.heightOf(_localWeather),
  PVVFL("[_localWeather]-space-[_verticalSeparator]-space-[_addLocation]"),
]).withViews(NSDictionaryOfVariableBindings(_localWeather, _verticalSeparator, _addLocation))
  .withMetrics(@{@"space": @11}).asArray];

同样Parus可以处理不正确的情况，例如

Constraint(_verticalSeparator, CenterY, Equal, _top, Width, +22)

和其他人。

如何在代码中处理NSLayoutConstraint冗长？

3 个答案: