如何在Xcode中添加此约束？看来我的relatedBy：论证是错误的 [英] How do I add this constraint in Xcode? It seems my relatedBy: argument is wrong

问题描述

我的代码如下，以及我的应用图片。基本上我想在 viewDidLoad 方法中为此视图控制器添加一个约束，以对齐两个标签，使它们从相同的x位置开始。无论出于何种原因，我都会收到此警告：

My code is below, as well as the image of my app. Basically I want to add a constraint in the viewDidLoad method for this view controller to align the two labels so they start at the same x position. For whatever reason, I'm getting this warning, though:

指向整数转换的不兼容指针将'UIView *'发送到类型'的参数NSLayoutRelation'（又名'enum NSLayoutRelation'）;

Incompatible pointer to integer conversion sending 'UIView *' to parameter of type 'NSLayoutRelation' (aka 'enum NSLayoutRelation');

当我运行应用程序时，我收到以下错误：

And when I run the app I get the following error:

*由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'* + [NSLayoutConstraint constraintWithItem：attribute：relatedBy：toItem：attribute：multiplier：constant：]：未知布局属性'

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:]: Unknown layout attribute'

NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:self.carMakeLabel attribute:NSLayoutRelationEqual relatedBy:self.view toItem:self.carModelLabel attribute:NSLayoutAttributeLeading multiplier:1.0 constant:0];

[self.view addConstraint:constraint];

推荐答案

尝试：

NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:self.carMakeLabel attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.carModelLabel attribute:NSLayoutAttributeLeading multiplier:1.0 constant:0];

[self.view addConstraint:constraint];

确保self.carModelLabel和self.carMakeLabel都在self.view的视图层次结构中。

Make sure self.carModelLabel and self.carMakeLabel are both in the view hierarchy of self.view.

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