是否可以基于另一个NSUserDefault值保存NSUserDefault值？

Question

Here is what I'm trying to achieve: I've location saved in NSUserDefaults. Now with this added in NSUserDefault user will select a value and I want to save this value in for this location. So when user selects that location again I can get the selected location back.

So this value is different for different locations and user can also change them at anytime. i want to know is it possible to do so? If not then what will be the optimized way to do this? I haven't started this implementation yet so there is no code.

Answer 1

If you want to save a dictionary:

let dict:[String:String] = ["key":"value"]
// set multiple values into a specific location
UserDefaults.standard.set(dict, forKey: "locationA")

// get the values for a given location
let result = UserDefaults.standard.value(forKey: "locationA")
print(result!)

or a simple value

let value = "value"

// set simple value into a specific location (for key)
UserDefaults.standard.set(value, forKey: "locationA")

// get the value for a given location
let result = UserDefaults.standard.value(forKey: "locationA")
print(result!)

Answer 2

It is possible to do this. For each location you could create a two-item NSArray in which the first item is the location, and the second item is the value. For example:

NSArray *locationData = @[location, value];

You would keep an NSArray of those two-item NSArrays , and save that to NSUserDefaults :

NSArray *allLocations = @[@[location1, value1], @[location2, value2], ...];
[[NSUserDefaults standardUserDefaults] setObject:allLocations forKey:@"LocationData"];

To look up the value for a particular location you would walk through the array (this code considers any location within 100m to be the same location):

- (id)valueForLocation:(CLLocation *)location {
    for (NSArray *locInfo in allLocations) {
        CLLocation *loc = (CLLocation *) locInfo[0];
        if ([location distanceFromLocation:loc] < 100) {
            return locInfo[1];
        }
    }
    return nil;
}

Another way to do this is to store this information in a dictionary, keyed off the location. You can't use a CLLocation as a key directly, but you put a CLLocation 's coordinates into an NSValue and use that. For more details see using CLLocation objects as keys in dictionary .