Question

I set base sdk 4.1 and ios deployment target = ios4.1. The contentScaleFactor is available in iOS 4.0 and later.

if ( [imageView respondsToSelector: @selector (contentScaleFactor:)] == YES )
{
    imageView.contentScaleFactor = 1.0;
}

Why do i always get NO ?

Answer 1

It does not respond to contentScaleFactor: because contentScaleFactor is a property, with the following accessors:

- (CGFloat)contentScaleFactor
- (void)setContentScaleFactor:(CGFloat)

There is no other method with the name contentScaleFactor that accepts a single parameter (marked by the :).

So, the selectors available are contentScaleFactor and setContentScaleFactor:. You are probably looking for setContentScaleFactor:, that’s what the setter is called.

Change your code to this:

if ( [imageView respondsToSelector:@selector(setContentScaleFactor:)] == YES )
{
    // Or as bbum says, use [imageView setContentScaleFactor:1.0];
    imageView.contentScaleFactor = 1.0;
}