New Object Instances are not running the Customized Initializer - ios

Question

I am working on a project that contains a Singleton instance of a class called Survey. Within that singleton instance is a property called "itemArray," which is an NSMutableArray that contains any number of instances of an Item class.
My Items class contains several NSInteger properties, but for the purposes of the application, I need to initialize all NSIntegers with a value of -1 instead of the default 0.
Now, for my Survey class (the one with the Singleton instance), I use the following method in the implementation to change the default value of a property:
-(id)init {
if (self = [super init]) {
_thingy = -1;
}
return self;
}
This works, but for some reason, the same exact syntax (with different properties) doesn't work for instances of my Item instances. For what it's worth, the following codeblock is the creation of 2 instances of Item, and their insertion into itemArray. I also tried the Item *item1 = [[Item alloc]init; method to no avail.
Item *item1;
[[[Survey sharedInstance]itemArray]insertObject:item1 atIndex:0];
Item *item2;
[[[Survey sharedInstance]itemArray]insertObject:item2 atIndex:1];
}
I would appreciate any assistance.
!!!!!UPDATE!!!!!
I entered the following conditional:
if (![[Survey sharedInstance]itemArray]){
NSLog(#"Test");
}
And the "test" logged onto the console, so it looks like the itemArray isn't being initialized. I'm not sure how to actually initialize it, though. When I try the following:
[[Survey sharedInstance]addressArray] = [[NSMutableArray alloc]init];
I'm getting an error saying "Expression is not assignable."
Survey.h:
#import <Foundation/Foundation.h>
#interface Survey : NSObject
+(instancetype)sharedInstance;
#property (nonatomic, strong) NSString *name;
#property (nonatomic, strong) NSString *emailAddress;
#property (nonatomic, assign) NSInteger trigger1;
#property (nonatomic, assign) NSInteger trigger2;
#property (nonatomic, assign) NSInteger trigger3;
#property (nonatomic, assign) NSInteger activeItem;
#property (nonatomic, strong) NSMutableArray *itemArray;
#end
Survey.m
#import "Survey.h"
#implementation Survey
+ (instancetype)sharedInstance {
static Survey *_instance;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_instance = [[Survey alloc] init];
});
return _instance;
}
-(id)init {
if (self = [super init]) {
_storage = -1;
}
return self;
}
#end

Answer 1

Instead of
[[Survey sharedInstance]addressArray] = [[NSMutableArray alloc]init];
you need to use
[Survey sharedInstance].addressArray = [[NSMutableArray alloc]init];
or
[[Survey sharedInstance] setAddressArray:[[NSMutableArray alloc]init]];
You were trying to assign a value to the return value of a getter method, which is not possible, so the compiler was saying "Expression not assignable." You need to use the setter method or dot notation instead.