保存NSArray

Question

我想将NSArray保存为文件或可能使用用户默认值.这是我希望做的.

1. 检索已保存的NSArray(如果有).
2. 用它做点什么.
3. 删除已保存的数据(如果有).
4. 保存NSArray.

这是可能的,如果是这样,我该怎么做？

Answer 1

NSArray为您提供了两种方法来完成您想要的任务:initWithContentsOfFile:和writeToFile:atomically:

一个简短的例子可能如下所示:

//Creating a file path under iOS:
//1) Search for the app's documents directory (copy+paste from Documentation)
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
//2) Create the full file path by appending the desired file name
NSString *yourArrayFileName = [documentsDirectory stringByAppendingPathComponent:@"example.dat"];

//Load the array
NSMutableArray *yourArray = [[NSMutableArray alloc] initWithContentsOfFile: yourArrayFileName];
if(yourArray == nil)
{
    //Array file didn't exist... create a new one
    yourArray = [[NSMutableArray alloc] initWithCapacity:10];

    //Fill with default values
}
...
//Use the content
...
//Save the array
[yourArray writeToFile:yourArrayFileName atomically:YES];

Answer 2

您可以对阵列包含的对象实施NSCoding,并使用NSKeyedArchiver将阵列序列化/反序列化为磁盘.

BOOL result = [NSKeyedArchiver archiveRootObject:myArray toFile:path];

归档程序将遵循您的NSCoding实现,以从每个对象获取可序列化的值,并编写可以使用NSKeyedUnarchiver读取的文件:

id myArray = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

序列化指南中的更多信息.