“Use of undeclared identifier”

Question

I'm pretty new to Objective C. Keep getting this error

"Use of undeclared identifier"

for this line of code:

NSString *textOut1 = textOut.text;

Obviously I am just trying to pull the textbox text. I have declared the following in my h file

@property (weak, nonatomic) IBOutlet UITextField *textOut;

So I cannot understand why I keep getting that damn error. Thanks!

Answer 1

Use this:

NSString *textOut1 = _textOut.text;

Checkout the extra underscore I added in front of textOut

Read the paragraph titled Most Properties Are Backed by Instance Variables in this apple documentation page.

Answer 2

To access the property textOut of an object referred to by the variable someVariable , you write someVariable.textOut . So to access the property textOut of the object that is self , you write self.textOut . You omitted the owner — self in this case.

Answer 3

If you are not (@synthesize) synthezising the property yourself then it will be synthesized with the instance variable having a Underscore at the start of the name.

try :

NSString *textOut1 = _textOut.text;

Answer 4

self.textOut.text is what you need.

A property is basically something like a class variable in Java that requires a public getter and setter to work with. So you cannot use it in a .m file directly, but need to utilize the getter and setter. Objective C on iOS actually provides you with these methods by itself. Hence, when you create a property, under the hood, you have code that does a getter and setter by itself.

You can set the value as :

_textOut = BLAHBLAH

And get it as :

[self textOut.text] 

or
self.textOut.text

or even _textOut.text (this is technically the local variable that is referenced by textOut )

Or in your case,

`NSString *textOut1 = [self textOut.text];`

or NSString *textOut1 = self.textOut.text;

or NSString *textOut1 = _textOut.text; // This is probably the least recommended one.

Though I believe the Stanford class says it is always better to do [self textOut] .