我在 NSUserDefaults 中的这个 NSMutableArray 结构做错了什么?“尝试插入非属性列表对象" [英] What am I doing wrong with this NSMutableArray of structs in NSUserDefaults? "attempt to insert non-property list object"

问题描述

我只是想在 NSUserDefaults 中保存 NSMutableArray/NSArray 的 struct 的 NSMutableArray:

I'm quite simply trying to save an NSMutableArray/NSArray of structs in NSUserDefaults:

typedef struct {
    int key;
} provision;

provision p1;
p1.key = 4;
NSValue *p1Value = [NSValue value:&p1 withObjCType:@encode(provision)];

provision p2;
p2.key = 5;
NSValue *p2Value = [NSValue value:&p2 withObjCType:@encode(provision)];

NSMutableArray *provisions = [[NSMutableArray alloc] init];
[provisions addObject:p1Value];
[provisions addObject:p2Value];

[[NSUserDefaults standardUserDefaults] setObject:provisions forKey:@"Provisions"];

我遵循了此处的指南，并将所有结构存储为 NSValue.但最后一行会导致运行时错误:

I followed the guide here and store all the structs as NSValue. But that last line causes a runtime error:

* 由于未捕获的异常NSInvalidArgumentException"而终止应用程序，原因:* -[NSUserDefaults setObject:forKey:]:尝试插入非属性列表对象("<04000000>",<05000000>") 为关键条款'

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[NSUserDefaults setObject:forKey:]: attempt to insert non-property list object ( "<04000000>", "<05000000>" ) for key Provisions'

我到底做错了什么?

推荐答案

来自 NSUserDefaults 类参考:

一个默认对象必须是一个属性列表，即(或对于集合实例的组合):NSData、NSString、NSNumber、NSDate、NSArray 或 NSDictionary.如果您想存储任何其他类型的对象，您通常应该将其存档以创建一个NSData 的实例.

A default object must be a property list, that is, an instance of (or for collections a combination of instances of): NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary. If you want to store any other type of object, you should typically archive it to create an instance of NSData.

发生异常是因为您尝试存储一个 NSValue 对象.要将结构存储为NSData，请使用

The exception occurs because you try to store an NSValue object. To store the struct as NSData, use

NSData *p1data = [NSData dataWithBytes:&p1 length:sizeof(p1)];

和提取它从NSData和

[p1data getBytes:&p1 length:sizeof(p1)];

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