从另一个NSDictionary创建NSDictionary？

Question

我有一个NSDictionary记录这个:

    address = "30 East 23rd Street";
    address1 = "30 East 23rd Street";
    address2 = "";
    age = 32;
    alert = "";
    "blood_pressure_1" = "";
    "blood_pressure_2" = "";
    bmi = "";

我想创建一个新的NSDictionary只包含从旧的几个键,如只是age,bmi和alert.我怎样才能做到这一点？

Answer 1

这可能会更容易一些:

NSArray *keys = [NSArray arrayWithObjects:@"address", @"address1", @"address2", nil];
NSDictionary *subset = [NSDictionary dictionaryWithObjects:
    [fullDictionary objectsForKeys:keys notFoundMarker:@""]
    forKeys:keys];