NSMutableArray初始化后未知

Question

I am trying to initialize an NSMutableArray depending on if one exists in NSUserDefaults or not using and if/else statement.

if ([[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"] == nil) {
    NSMutableArray *customers = [NSMutableArray arrayWithCapacity:10];
} else {
    NSMutableArray *customers = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"]mutableCopy];
}

Customer *c = [[Customer alloc]init];

c.fName = self.fnameTextField.text;
c.lName = self.lnameTextField.text;
c.username = self.usernameTextField.text;
c.balance = [self.depositTextField.text floatValue];

[customers addObject:c];

[[NSUserDefaults standardUserDefaults] setObject:customers forKey:@"customers"];
[[NSUserDefaults standardUserDefaults] synchronize];

When trying to add an object to the array, I get "Unknown receiver 'customers.'" I'm not sure why I'm not able to use the array.

Answer 1

Try declaring the customers array outside your if statement

NSMutableArray *customers;
if ([[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"] == nil) {
   customers = [NSMutableArray arrayWithCapacity:10];
} else {
   customers = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"]mutableCopy];
}

Answer 2

I am quite sure you have written it like this,

NSMutableArray *customers;

if ([[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"] == nil) {
    NSMutableArray *customers = [NSMutableArray arrayWithCapacity:10];
} else {
    NSMutableArray *customers = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"]mutableCopy];
}

So, what is wrong here?

Note that if and else create their own scope, so the variable you declare inside if and else are new variable, not the one from outer scope. If you want to use customers from outer scope, do it like this,

NSMutableArray *customers;

if ([[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"] == nil) {
   customers = [NSMutableArray arrayWithCapacity:10];
} else {
   customers = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"customers"] mutableCopy];
}

Now, customers inside if and else block is the same variable that you have declared outside the if/else block.