object return empty description in iOS - ios

Question

hello I am doing something like this.
NSString * fblink=[dm.commonDataArray valueForKey:#"fb_link"];
if(![fblink isEqual:[NSNull null]]||![fblink isEqualToString:#""]||![fblink length]<=0)
{
[fb_button setImage:[UIImage imageNamed:#"ico_user_fb"] forState:UIControlStateNormal];
[fb_button addTarget:self
action:#selector(buttonFBTouch:)
forControlEvents:UIControlEventTouchUpInside];
}else{
[fb_button setImage:[UIImage imageNamed:#"ico_fb_red_gray"] forState:UIControlStateNormal];
}
when I type fblink in my log it says (lldb) po fblink
<object returned empty description> But still my if condition become true and go inside ratherthan going to else part.
How can I overcome this problem?I dont want to execute my if condition true part if its return empty description. How can I checked this condition? Please help me
Thanks

Answer 1

The problem is with your if condition. fblink is nil, you are checking nil is equal to [NSNull null] so this case fails and you invert the result so it becomes true and goes inside of this if case.
If we expand your if case it becomes:
if(![nil isEqual:[NSNull null]]||![nil isEqualToString:#""]||![nil length]<=0)
{
}
Which becomes
if(!false||!false||!true) // which evaluates to true, you are using ||, so if any one condition is true, it will go inside of the if case
{
}
You need to change that if case to:
if([fblink isKindOfClass:[NSString class]] && ![fblink length]<=0)
{
}
else
{
}

Answer 2

you can try.....
if(![fblink isEqual:[NSNull null]]&&![fblink isEqualToString:#""]&&![fblink length]<=0)
{
//your code here .......
}
else
{//your code here ...}

Answer 3

I think that the fblink is not null but its an empty string. Thus your ![fblink isEqual:[NSNull null]] is becoming true and your if statement is getting executed. Only check it with the following condition:
if(![fblink isEqualToString:#""]||![fblink length]=0)

Answer 4

You have to change the || (or) condition to &&(and) condition.
Try this:
if(![fblink isEqual:[NSNull null]]&&![fblink isEqualToString:#""]&&![fblink length]<=0 )
{
//your code
}
else
{
// your code
}