ios - 具有 NSNumber 到 NSString 映射的 NSDictionary 是非属性列表对象

Question

以下代码:

[[NSUserDefaults standardUserDefaults] setObject:photoIdToPath forKey:@"photo_id_to_path"];

给我以下错误:

Attempt to set a non-property-list object {
417675729 = "/Users/k06a/Library/Application Support/iPhone Simulator/7.1/Applications/21163736-DF6F-4E79-8196-6A966C81ED1B/Documents/417675729";
} as an NSUserDefaults value for key photo_id_to_path

这里是 Xcode 调试控制台的 photoIdToPath 字典内容分析:

(lldb) po photoIdToPath
{
    417675729 = "/Users/k06a/Library/Application Support/iPhone Simulator/7.1/Applications/21163736-DF6F-4E79-8196-6A966C81ED1B/Documents/417675729";
}

(lldb) po [[[photoIdToPath allKeys] lastObject] class]
__NSCFNumber

(lldb) po [[[photoIdToPath allValues] lastObject] class]
NSPathStore2

所以NSPathStore2是NSString的子类，为什么这个字典不是属性列表？

更新:

在这里https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/nsuserdefaults_Class/Reference/Reference.html#//apple_ref/occ/instm/NSUserDefaults/setObject:forKey : 我找到了文字:

The value parameter can be only property list objects: NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary. For NSArray and NSDictionary objects, their contents must be property list objects. See “What is a Property List?” in Property List Programming Guide.

Answer 1

将字典保存到 NSUserDefaults 的唯一方法(或将字典作为 plist 写入文件)，所有键必须是 NSString 对象，所有值必须是有效的 plist 对象。

换句话说，您不能拥有作为NSNumber 对象的键。如果您需要将字典写入 NSUserDefaults，请将它们转换为 NSString。

有关这方面的详细信息，请参阅 Property List Programming Guide .特别是标题为 What is a Property List? 的部分.有一个表格显示了所使用的 XML 标签。在该表下，您将看到以下摘录:

And although NSDictionary and CFDictionary objects allow their keys to be objects of any type, if the keys are not string objects, the collections are not property-list objects.