macOS Objective-C help with NSMutableArray

#import <Cocoa/Cocoa.h>
#import "NewTable.h"

@interface AppDelegate : NSObject <NSApplicationDelegate,NSTableViewDelegate>
{
    NSInteger at;
    int count;
    NSMutableArray *list;
}

@property (assign) IBOutlet NSWindow *window;

@property (assign) IBOutlet NSTextField *input;
@property (assign) IBOutlet NSButton *add;
@property (assign) IBOutlet NSButton *remove;
@property (assign) IBOutlet NSTableView *table;

-(IBAction)addToList:(id)sender;
-(IBAction)removeFromList:(id)sender;
-(IBAction)checkList:(id)sender;

@end

#import "AppDelegate.h"

@implementation AppDelegate

@synthesize window = _window;
@synthesize add;
@synthesize remove;
@synthesize input;
@synthesize table = _table;

- (void)dealloc
{
    [list release];
    [super dealloc];
}
-(id)init
{
    [super init];
    at=0;
    count=1;
    list = [[NSMutableArray alloc] init];
    NSString *var = @"Type something";
    [list addObject:var];
    return self;
}
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    // Insert code here to initialize your application
}


-(void)tableView:(NSTableView *)aTableView setObjectValue:(id)object forTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{
    
}
- (int)numberOfRowsInTableView:(NSTableView *)tableView
{
    NSLog(@"numberOfRowsInTableView called");
    return count;
}
- (id)tableView:(NSTableView *)tableView
objectValueForTableColumn:(NSTableColumn *)tableColumn
            row:(int)row
{
    NSLog(@"objectValueForTableColumn called");
    at = [_table clickedRow];
    if((int)at > count) at = (NSInteger) count;
    else if(at<0) at = 0;
    if(!count || (row>count))
    {
        return @"";
    }
    else
    {
        return [list objectAtIndex:row];
    }
}



-(void)tableViewSelectionDidChange:(NSNotification *)notification
{
    NSInteger row = [_table selectedRow];
    if(row==-1)
    {
        return;
    }
    else
    {
        at = row;
    }
}

-(IBAction)addToList:(id)sender
{
    NSLog(@"addToList click registered, at=%ld, count=%i",at,count);
    [list insertObject:[NSString stringWithString:[input stringValue]] atIndex:at];
    count++;
}
-(IBAction)removeFromList:(id)sender
{
    NSLog(@"removeFromList click registered at=%ld, count=%i",at,count);
    if(at<count)
    {
        NSString *var = [list objectAtIndex:at];
        [list removeObjectAtIndex:at];
        [var release];
        count--;
    }
}

-(IBAction)checkList:(id)sender
{
    NSString *the_list = [[NSString alloc] initWithString:@"List: "];
    for (NSString *var in list)
    {
        [the_list stringByAppendingFormat:@"%@, %@",the_list,var];
    }
    NSLog(the_list);
    [the_list release];
}

-(void)awakeFromNib
{
    NSIndexSet *indices = [NSIndexSet indexSetWithIndex:1];
    [_table selectRowIndexes:indices byExtendingSelection:NO];
    [_table scrollRowToVisible:1];
    at = count;
}
@end

for(NSString *var in list)

[list insertObject:[NSString stringWithString:[input stringValue]] atIndex:at];