Question

我编写了一些从plist文件中提取信息的代码，并做了一些事情，然后最终将这些数据弹出到表中。

这一切都运行正常，问题是我编写了从资源文件夹中的plist文件中提取数据的代码，但实际文件将通过动作创建并存储在内存中。我需要一些帮助，以便在从新位置拉出代码时使我的代码正常工作。

当前的工作代码：

- (void) loadData{
// Load items
NSString *error;
NSPropertyListFormat format;
NSString *path = [[NSBundle mainBundle] pathForResource:@"CalculatorData" ofType:@"plist"];
NSData *plistData = [NSData dataWithContentsOfFile:path];
NSArray *amountData = [NSPropertyListSerialization propertyListFromData:plistData mutabilityOption:NSPropertyListImmutable format:&format errorDescription:&error];
NSDictionary *amountData = [NSPropertyListSerialization propertyListFromData:plistData mutabilityOption:NSPropertyListImmutable format:&format errorDescription:&error];

if (amountData) {
    self.amounts = [[NSMutableArray alloc] initWithCapacity:[amountData count]];
    result = 0;
    for (NSDictionary *amountsDictionary in amountData) {

        [self.amounts addObject:amountsDictionary];

        currentNumber = [[amountsDictionary objectForKey:@"Value"] floatValue];

        if ([[amountsDictionary objectForKey:@"Type"] isEqualToString:@"Plus"]) {
            result = result + currentNumber;
        } else {
            result = result - currentNumber;
        }
    }
    //Set main amount
    NSString *msg = [NSString stringWithFormat:@"£%.2f",result];
    [lblAmount setText:msg];
} else {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"Why not keep track of your income and expensies? Add new items below." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    [alert release];
}
}

我想从新文件位置提取信息我需要类似下面的内容，但似乎无法获得与上面相同的输出：

//Get file location
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"saveBudget.plist"];

// read it back in with different dictionary variable
NSMutableDictionary *amountData = [NSMutableDictionary dictionaryWithContentsOfFile:path];
if(amountData==nil ){
    NSLog(@"failed to retrieve dictionary from disk");
} else {  
    NSLog(@"%@", amountData);
}

创建plist文件的代码是（这也需要一些工作，因为它当前总是覆盖以前做过的，当我希望它添加一个新数组时）：

-(void) addData {

// create a dictionary to store a fruit's characteristics
NSMutableDictionary *items = [[NSMutableDictionary alloc] init];
[items setObject:@"10" forKey:@"Value"];
[items setObject:@"tester" forKey:@"Description"];
[items setObject:@"Plus" forKey:@"Type"];

// create a dictionary to store all fruits
NSMutableDictionary *plist = [[NSMutableDictionary alloc] init];
[plist setObject:items forKey:@"0"];

//Get file location
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"saveBudget.plist"];

// write plist to disk
[plist writeToFile:path atomically:YES];
}

这也需要我想做的一点工作：

    <?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>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
</array>
</plist>

对于长篇文章感到抱歉，但希望应该是所有相关的内容。对此的任何帮助都会很棒。

Answer 1

如果您希望plist的最外层元素是一个数组，那么您发布的代码中的以下行将创建一个错误类型的对象：

// create a dictionary to store all fruits
NSMutableDictionary *plist = [[NSMutableDictionary alloc] init];
[plist setObject:items forKey:@"0"];

我还要注意在代码中留下过时的评论声明，因为它们有时会让你误导自己。这是建议的addData方法重写：

-(void)addData {

    // Create a dictionary representing an item
    //
    NSDictionary *item = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"10", @"Value",
                          @"tester", @"Description",
                          @"Plus", @"Type",
                          nil];

    // Create an array of items. This must be an instance of NSArray or
    // NSMutableArray if you want the corresponding element in your plist
    // to be an array.
    //
    NSArray *items = [NSArray arrayWithObjects: item, nil];

    // Get file location (this part is fine).
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"saveBudget.plist"];

    // Write array of items to filesystem
    [items writeToFile:path atomically:YES];
}

道歉，我没有测试过上面的代码，但它至少应该用来说明这一点。

字典和plist文件

1 个答案: