Need help with UISearchBar and NSString

I would like to make an if command that checks the value of my UISearchBar in that way if the value of the UISearchBar is equals to " " or multiple spaces without words and chars, an alert will popup. Well, I don't need help with the creation of the alert but I do need help with the if command and th开发者_如何转开发e spaces. I know how to do it with multiple "if" command but I want with only 1.

Thanks!

If I'm understanding the question correctly, you want to check for whitespace.

if ([[theSearchBarText stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0){
    // Search string is empty
}