macOS changing NSTextView string value

#import <Cocoa/Cocoa.h>

@interface AppDelegate : NSObject <NSApplicationDelegate>
@property (assign) IBOutlet NSWindow *window;

@property (weak) IBOutlet NSButton *button1;
@property (weak) IBOutlet NSButton *button2;
@property (weak) IBOutlet NSButton *button3;
@property (weak) IBOutlet NSTextView*textfield;

#import "AppDelegate.h"

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    // Insert code here to initialize your application
}


- (IBAction)button1:(id)sender{
   _textfield.stringValue = @"exampletext1";
}

- (IBAction)button2:(id)sender{
    _textfield.stringValue = @"exampletext2";
}

- (IBAction)button3:(id)sender{
    _textfield.stringValue = @"exampletext3";
}

@property (weak) IBOutlet NSTextView*textfield;

- (IBAction)button1:(id)sender{
   _textfield.stringValue = @"exampletext3";
}

- (IBAction)button2:(id)sender{
    _textfield.stringValue = @"exampletext2";
}

- (IBAction)button3:(id)sender{
    _textfield.stringValue = @"exampletext3";
}

@property (weak) IBOutlet NSTextView*textfield;

@property (weak) IBOutlet NSTextField *textfield;

#import <Cocoa/Cocoa.h>

@interface testAppDelegate : NSObject <NSApplicationDelegate> {
    
    IBOutlet NSTextView *textView;
}
@property (assign) IBOutlet NSWindow *window;

- (IBAction)button1:(id)sender;
- (IBAction)button2:(id)sender;
@end

#import "testAppDelegate.h"

@implementation testAppDelegate

@synthesize window;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    // Insert code here to initialize your application
}

-(void)awakeFromNib
{
    NSString *myString = @"this is a string";
    [textView insertText:myString];
}


- (IBAction)button1:(id)sender {
    [textView setString:@"String number 1111111"];
    NSString *myString = [textView string];
}

- (IBAction)button2:(id)sender {
    [textView setString:@"String number 2222222"];
    NSString *myString = [textView string];
}
@end

 NSString *myString = [textView string];

#import <Cocoa/Cocoa.h>

@interface testAppDelegate : NSObject <NSApplicationDelegate> {
    
    IBOutlet NSTextView *textView;
}
@property (assign) IBOutlet NSWindow *window;

- (IBAction)button1:(id)sender;
- (IBAction)button2:(id)sender;
@end

#import "testAppDelegate.h"

@implementation testAppDelegate

@synthesize window;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    // Insert code here to initialize your application
}

-(void)awakeFromNib
{
    NSString *myString = @"this is a string";
}


- (IBAction)button1:(id)sender {
    [textView setString:@"whatever"];
}

- (IBAction)button2:(id)sender {
    [textView setString:@"abcdefg"];
}
@end

[textView insertText:myString];