“NSInvalidArgumentException'的，理由是：”无法解析约束格式“ [英] 'NSInvalidArgumentException', reason: 'Unable to parse constraint format'

问题描述

我有我想要旋转屏幕期间保持停止子视图，所以我决定把NSLayoutConstraint类型：



尾随空格来的SuperView

顶层空间，以上海华

按钮空间来的SuperView


我在的UITableViewCell的子类。我写了code，但我得到以下错误：

 'NSInvalidArgumentException'的，理由是：无法解析约束格式：
 自不在次字典的关键。
 H：[self.arrows] -5- |
 

在CustomCell.m我的code是：

  self.arrows = [[箭头的alloc] initWithFrame：方法CGRectMake（self.contentView.bounds.size.width-30，self.bounds.origin.y + 4，30，自.contentView.bounds.size.height-4）]; *的NSDictionary = viewsDictionary NSDictionaryOfVariableBindings（self.arrows，self.contentView）;
 NSMutableArray里*约束= [[NSMutableArray里的alloc]初始化];
 [约束addObjectsFromArray：[NSLayoutConstraint constraintsWithVisualFormat：@H：[self.arrows] -5 |选项​​：0的指标：无意见：viewsDictionary]];
 [约束addObjectsFromArray：[NSLayoutConstraint constraintsWithVisualFormat：@V：| -1- [self.arrows]选项：0的指标：无意见：viewsDictionary]];
 [约束addObjectsFromArray：[NSLayoutConstraint constraintsWithVisualFormat：@[V：[self.arrows] -1- |选项​​：0的指标：无意见：viewsDictionary]];
 [self.arrows addConstraints：约束];
 

解决方案

它看起来像的自动布局可视化格式解析引擎是间preting了。在VFL约束像它的使用是一个的keyPath而不是关键 valueForKeyPath：

NSDictionaryOfVariableBindings（...）将采取一切你的参数是在括号，并把它翻译成与该对象的值字面键（在您的情况： @ {self.arrow：self.arrow} ）。在VFL的情况下，自动布局在想，你有一个关键的名为自在你看来字典使用具有<$ C $的关键一子字典（或子对象） C>箭头，

  @ {
   @自我：@ {@箭头：self.arrow}
}
 

当你从字面上希望系统间preT你的密钥为 self.arrow

通常，当我使用一个实例变量吸气剂这样的，我通常最终会创造我自己的字典，而不是使用 NSDictionaryOfVariableBindings（...），如下所示：

 的NSDictionary *意见= @ {@arrowView：self.arrow}
 

或

 的NSDictionary *意见= NSDictionaryOfVariableBindings（_arrow）;
 

这将允许您使用您的VFL认为没有自我，你还知道你在说什么：

 的NSArray * arrowHorizCons​​traints = [NSLayoutConstraint constraintsWithVisualFormat：@H：[arrowView] -5 |选项​​：0的指标：无意见]。
 

或

 的NSArray * arrowHorizCons​​traints = [NSLayoutConstraint constraintsWithVisualFormat：@H：[_箭头] -5 |选项​​：0的指标：无意见]。
 

作为一般规则，我已经学会不要有字典键用点（。），在其中，以避免任何混乱的系统或调试的噩梦。

I have a subview that I want to keep stops during rotating screen, so I decided to put the NSLayoutConstraint type:

Trailing Space to Superview
Top Space to Superview
Button Space to Superview
I'm in a subclass of UITableViewCell. I wrote the code but I get the following error:

'NSInvalidArgumentException', reason: 'Unable to parse constraint format: 
 self is not a key in the views dictionary. 
 H:[self.arrows]-5-|

My code in CustomCell.m is:

 self.arrows = [[Arrows alloc]initWithFrame:CGRectMake(self.contentView.bounds.size.width-30, self.bounds.origin.y+4, 30, self.contentView.bounds.size.height-4)];

 NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(self.arrows, self.contentView);
 NSMutableArray * constraint=[[NSMutableArray alloc]init];
 [constraint addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:  [self.arrows]-5-|" options:0 metrics:nil views:viewsDictionary]];
 [constraint addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-1-[self.arrows]" options:0 metrics:nil views:viewsDictionary]];
 [constraint addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"[V: [self.arrows]-1-|" options:0 metrics:nil views:viewsDictionary]];
 [self.arrows addConstraints:constraint];

解决方案

It looks like that the autolayout visual format parsing engine is interpreting the "." in your VFL constraint to be a keyPath instead of a key like it's using valueForKeyPath:.

NSDictionaryOfVariableBindings(...) will take whatever your parameter is in the parenthesis and translate it into a literal key with the object as the value (in your case: @{"self.arrow" : self.arrow}). In the case of the VFL, autolayout is thinking that you have a key named self in your view dictionary with a subdictionary (or subobject) that has a key of arrow,

@{
   @"self" : @{ @"arrow" : self.arrow }
}

when you literally wanted the system to interpret your key as "self.arrow".

Usually, when I'm using a instance variables getter like this, I typically end up creating my own dictionary instead of using NSDictionaryOfVariableBindings(...) like so:

NSDictionary *views = @{ @"arrowView" : self.arrow }

or

NSDictionary *views = NSDictionaryOfVariableBindings(_arrow);

Which would allow you to use the view in your VFL without the self and you still know what you're talking about:

NSArray *arrowHorizConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[arrowView]-5-|" options:0 metrics:nil views];

or

NSArray *arrowHorizConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[_arrow]-5-|" options:0 metrics:nil views];

As a general rule, I've learned not to have dictionary keys with a dot (.) in them to avoid any system confusion or debugging nightmares.

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