objective-c - 如何使用 arrayWithContentsOfFile 加载在 ObjectiveC/XCode 中用 writeToFile 成功写入的文件

Question

我正在将一组自定义对象保存到 plist 列表文件中，如下所示:

+(void) arrayToPlist: (NSArray*) plant_types{
    NSMutableArray* dictionary_array = [NSMutableArray arrayWithCapacity: plant_types.count];

    for(int i = 0; i<plant_types.count; i++){
        PlantType* pt = [plant_types objectAtIndex: i];
        [dictionary_array addObject: [pt toDict]];
    }

    NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString* filePath    = [rootPath stringByAppendingPathComponent:@"PlantTypes.plist"];
    NSLog(@"Writing plist to: %@", filePath);

    [dictionary_array writeToFile: filePath atomically: YES];  
}

创建的文件如下所示:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<array>
    <dict>
        <key>name</key>
        <string>Autumn Olive</string>
        <key>radius</key>
        <real>10</real>
    </dict>
    <dict>
        <key>name</key>
        <string>Dwarf Cherry</string>
        <key>radius</key>
        <real>5</real>
    </dict>
    <dict>
        <key>name</key>
        <string>Bamboo</string>
        <key>radius</key>
        <real>2</real>
    </dict>
    <dict>
        <key>name</key>
        <string>Pomegranate</string>
        <key>radius</key>
        <real>6</real>
    </dict>
    <dict>
        <key>name</key>
        <string>Lupin</string>
        <key>radius</key>
        <real>0.60000002384185791</real>
    </dict>
</array>
</plist>

并以这种方式加载它们:

+(NSMutableArray*) arrayFromPlist{
    NSLog(@"Loading array of plant types from plist.");

    NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString* filePath    = [rootPath stringByAppendingPathComponent:@"PlantTypes.plist"];
    NSFileManager*  fileManager = [NSFileManager defaultManager];

    if([fileManager fileExistsAtPath:filePath]){ 
        NSLog(@"Plist file exists at expected location.");
        NSMutableArray* plant_dicts = [NSMutableArray arrayWithContentsOfFile:filePath];
        NSLog(@"Loaded array with contents of file, got %d plant types.", plant_dicts.count);
        NSMutableArray* plant_types = [NSMutableArray arrayWithCapacity: plant_dicts.count];
        for(int i = 0; i< plant_dicts.count; i++){
            NSMutableDictionary* dict = [plant_dicts objectAtIndex: i];
            [plant_types addObject: [PlantType fromDict: dict]];
        }
        return plant_types;
    }
    NSLog(@"Plant Type plist file not found.");
    return NULL;
}

没有崩溃，但每次我返回一个大小为零的 NSMutableArray(并且日志语句确认 plant_dicts 的大小为零)。

我做错了什么？我在 arrayWithContentsOfFile: 中看到的所有类似问题都是人们手动或使用编辑器创建 plist 的......我认为从代码本身制作它不会有这些问题...... .

编辑:我已经确认我不再得到大小为零的结果(这很奇怪，自原始帖子以来该部分没有代码更改)。但是，我仍然没有正确加载东西。这是我的 fromDict 和 toDict 方法。

问题是字符串“shape”似乎加载不正确。至少，当我询问 shape == @"Circle"是否存在时，我得到它不存在，即使它在 NSLog 语句中明确存在。我在代码的其他地方进行了相同的比较(当检查如何呈现对象时)并且它在那里工作正常(所以我假设没有像 Java 中那样奇怪的 == vs .equals)。

双重编辑:等等，没有 [shape isEqualToString: @"Circle"]...为什么我之前不需要使用它让我感到困惑，但在这里添加它会有所帮助。

Answer 1

使用您的 plist，此代码返回正确的结果

+(NSMutableArray*) arrayFromPlist{
    NSLog(@"Loading array of plant types from plist.");

    NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString* filePath    = [rootPath stringByAppendingPathComponent:@"PlantTypes.plist"];
    NSFileManager*  fileManager = [NSFileManager defaultManager];

    if([fileManager fileExistsAtPath:filePath]){ 
        NSLog(@"Plist file exists at expected location.");
        NSMutableArray* plant_dicts = [NSMutableArray arrayWithContentsOfFile:filePath];
        NSLog(@"Loaded array with contents of file, got %d plant types.", plant_dicts.count);
        NSMutableArray* plant_types = [NSMutableArray arrayWithCapacity: plant_dicts.count];
        for(int i = 0; i< plant_dicts.count; i++){
            NSMutableDictionary* dict = [plant_dicts objectAtIndex: i];
            [plant_types addObject: dict];
        }
        return plant_types;
    }
    NSLog(@"Plant Type plist file not found.");
    return NULL;
}

结果

2012-02-22 16:24:43.697 Test[5574:10103] Loading array of plant types from plist.
2012-02-22 16:24:43.698 Test[5574:10103] Plist file exists at expected location.
2012-02-22 16:24:43.699 Test[5574:10103] Loaded array with contents of file, got 5 plant types.
2012-02-22 16:24:43.700 Test[5574:10103](
        {
        name = "Autumn Olive";
        radius = 10;
    },
        {
        name = "Dwarf Cherry";
        radius = 5;
    },
        {
        name = Bamboo;
        radius = 2;
    },
        {
        name = Pomegranate;
        radius = 6;
    },
        {
        name = Lupin;
        radius = "0.6000000238418579";
    }
)

我认为问题出在您的 PlantType 实现上。你能发布你的代码吗(toDict 和 fromDict 方法)