How to check if a UITextfield has Text in it? - iphone

Question

I just followed a tut on making a conversion app. It was good, but I wanted to expand on it. The tut has you input a value in for Fahrenheit and then converts to Celsius. Pretty basic. So I wanted to add a Kelvin conversion as well. But the code only let you plug in a number for the Fahrenheit. So after adding the Kelvin text field, I wanted to check to see which text box had text in it. So I used the following code:
- (IBAction)convert:(id)sender
{
if ([fahrenheit isFirstResponder])
{
float x = [[fahrenheit text] floatValue];
float y = (x - 32.0f) * (5.0f/9.0f); //celcius
float z = y + 273.15f; //kelvin
[celcius setText:[NSString stringWithFormat:#"%3.2f" , y]];
[kelvin setText:[NSString stringWithFormat:#"%3.2f" , z]];
[fahrenheit resignFirstResponder];
} else if ([celcius isFirstResponder])
{
float x = [[celcius text] floatValue];
float y = 32.0f + ((9.0f/5.0f) * x); //farenheit
float z = x + 273.12f; //kelvin
[fahrenheit setText:[NSString stringWithFormat:#"%3.2f" , y]];
[kelvin setText:[NSString stringWithFormat:#"%3.2f" , z]];
[celcius resignFirstResponder];
}else if ([kelvin isFirstResponder])
{
float x = [[kelvin text] floatValue];
float y = x - 273.15f; //celcius
float z = 32.0f + ((9.0f/5.0f) * y); //farenheit
[celcius setText:[NSString stringWithFormat:#"%3.2f" , y]];
[fahrenheit setText:[NSString stringWithFormat:#"%3.2f" , z]];
[kelvin resignFirstResponder];
}
}
This allowed me to input a number in any text field and then convert. But then I decided to dismiss the keyboard. My code said to resignFirstResponder. But then the convert action did not work because now there was no first responder. Any clues as to how I can check which text box has text in it, and then do the conversions? Thanks in advance for any help.

Answer 1

if( [textField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] != nil && [textField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] != #"" )
{
// text field has text
// get text without white space
NSString * textWithoutWhiteSpace = [textField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
}

Answer 2

This is for checking textView is empty or not:-
if([textView.text isEqualToString:#""])
{
//textView is Empty
}
else
{
//textView has text
}
If you want to check it for white space as well, first remove white spaces from string then check ... like this -
NSString *trimmedString = [tV.text stringByTrimmingCharactersInSet:
[NSCharacterSet whitespaceAndNewlineCharacterSet]];
if([trimmedString isEqualToString:#""])
{
NSLog(#"textView is empty");
}
else
{
NSLog(#"textView has some value");
}

Answer 3

Just use the hasText method.
Example:
if(_yourTextField.hasText)
{
// Do something.
}

Answer 4

if(textView.text.length > 0)
{
//text present
}
else
{
//no text
}

Answer 5

Better solution is make all conversions on the fly, add new action to all textFields
[textField addTarget:self action:#selector(textChanged:) forControlEvents:UIControlEventEditingChanged];
Then in method textChanged: do something like this:
- (void) textChanged:(UITextField *)tf {
if (tf.text.floatValue > 0) {
if (tf == fahrenheit) {
//Do convertion for fahrenheit
}
.
.
.
//etc.
}
}

Answer 6

On response to Meno's answer
DO NOT USE != #""
this check for pointer equality vs String equality
use:
[string isEqualToString:#""];

Answer 7

If you want to know it DURING input, and probably performs actions based on this info, you shall use:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

Answer 8

There were a few problems in some of the other answers, like they didn't use isEqualToString, and they superfluously removed potential characters from a string that we are only interested in if it is nil or not.
I don't have enough reputation to comment, so I am posting this as an answer.
For a similar issue, I used this to check each textfield that I needed to check for being empty:
- (BOOL) isEmpty:(UITextField*) field
{
if (!(field.text) ||
([[field.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] isEqualToString: #""]))
{
return YES;
}
else
{
return NO;
}
}

Answer 9

If you need an NSString with white space removed:
NSString *nonWhiteSpaceString = [textfield.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
Then you could use the length as a boolean:
BOOL textFieldHasText = nonWhiteSpaceString.length;