与Interface Builder的链接较弱 [英] Weak linking with Interface Builder

问题描述

应用程序使用3.x SDK功能，但需要在2.x设备中运行。解决方案似乎是使用弱链接，我做了，但应用仍然无法*编译*为iPhone 2.2.1：框架未找到MapKit。

Application uses 3.x SDK feature, but needs to run in 2.x devices. The solution seems to be using "weak linking", which I did, but app still fails to * compile * for iPhone 2.2.1: "Framework not found MapKit".

编译目标Device 3.0 - Debug即可，甚至安装在运行2.2.1的iPod Touch上！只要我没有使用MapKit激活视图就运行正常，如果我没有崩溃。

Compile for target "Device 3.0 - Debug" is ok, even installs on my iPod Touch running 2.2.1! Runs ok as long as I don't activate view using MapKit, crashes if I do.

我使用Interface Builder创建了一个视图，在其上拖动了一个MkMapView对象。据我所知，这是对MapKit的唯一引用，所以问题是：当我使用弱链接时，我可以在IB中使用相关的UI元素吗？我应该只在XCode中完成所有这些吗？猜对了，但是能够在2.2.1设备上安装和运行3.0应用程序会让我困惑......

I created a view using Interface Builder, dragged a MkMapView object on it. As far as I can tell, this is the only reference to MapKit, so the question is: when I use weak linking, can I use related UI elements in IB at all? Should I do all of this in XCode only? Guess yes, but being able to install and run "3.0" app on "2.2.1" device confuses me...

推荐答案

您不应该在2.0设备上加载仅包含3.0对象（如MKMapView）的nib文件。这意味着，您必须从代码中检查您在nib中使用的框架/类的可用性。如果它们不可用，则不得加载笔尖。

You should not load a nib file which contains 3.0 only objects like MKMapView on a 2.0 device. That means, you have to check from code the availability of the framework/classes you use in the nib. If they are not available, you must not load the nib.

这是检查地图套件是否可用的方法：

This is how you can check if map kit is available:

if (NSClassFromString(@"MKMapView") != NULL) {
    // load nib, map kit is available
} else {
    // do something else, map kit is not there
}

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