Question

每当我保存数据时，我都有一个代码将数据添加到plist文件对象中。他们早先粉碎了！

除了更多我还想要他们！这怎么可能？

我保存数据的代码：

// get paths from root direcory
    NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
    // get documents path
    NSString *documentsPath = [paths objectAtIndex:0];
    // get the path to our Data/plist file
    NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"Data.plist"];

    // set the variables to the values in the text fields
    self.personName = nameEntered.text;
    self.phoneNumbers = [[NSMutableArray alloc] initWithCapacity:3];
    [phoneNumbers addObject:homePhone.text];
    [phoneNumbers addObject:workPhone.text];
    [phoneNumbers addObject:cellPhone.text];


    // create dictionary with values in UITextFields
    NSDictionary *plistDict = [NSDictionary dictionaryWithObjects: [NSArray arrayWithObjects: personName, phoneNumbers, nil] forKeys:[NSArray arrayWithObjects: @"Name", @"Phones", nil]];

    NSString *error = nil;
    // create NSData from dictionary
    NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:plistDict format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];

    // check is plistData exists
    if(plistData) 
    {
        // write plistData to our Data.plist file
        [plistData writeToFile:plistPath atomically:YES];
    }
    else 
    {
        NSLog(@"Error in saveData: %@", error);
        [error release];
    }

Answer 1

每次都使用新数据覆盖plist文件。如果要附加，则需要先从plist文件加载现有数据，然后将新数据添加到该字典中，然后写出更新后的字典。

Answer 2

阅读plistPath的内容：
NSMutableData * myData = [NSMutableData dataWithContentsOfFile：plistPath];
并改变这一点：

// create NSData from dictionary
NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:plistDict format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];

到：

// create NSData from dictionary
NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:plistDict format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];  
[myData appdendData:plistData];

最后将myData写入文件。

希望有所帮助！

为什么要删除而不是添加.plist

2 个答案: