how to set NSGradient to NSWindow background

I am new to cocoa I am try to set NSGradient to the NSWindow background but it's too difficult for me...I have try this code

NSGradient *gradient = [[NSGradient alloc] initWithStartingColor:[NSColor orangeColor] endingColor:[NSColor lightGrayColor]];
NSRect windowFrame = [self frame];
[gradient drawInRect:windowFrame angle:90];

but it is not working.... any other way to set NSGradient to NSWindow....

You can do it by subclassing NSWindow's View.

Create new window view's class (For example with title WindowViewSubclass).

Then .h file should look like this:

#import <Cocoa/Cocoa.h>

@interface WindowViewSubclass : NSView {

}

@end

and .m file:

#import "WindowViewSubclass.h"

@implementation WindowViewSubclass

- (void)drawRect:(NSRect)dirtyRect
{
    NSGradient *gradient = [[NSGradient alloc] initWithStartingColor:[NSColor orangeColor] endingColor:[NSColor lightGrayColor]];
    NSRect windowFrame = [self frame];
    [gradient drawInRect:windowFrame angle:90];
}

@end

Now select window's view and go to Identity Inspectory -> Custom Class -> and select class like this:

Result: