检查是否使用参数调用函数

Question

Codeigniter has a syntax for url parameter passing for functions inside the controller.

If a function for example:

function index($id){
     $this->model->get_user($id);
}

Assuming that this function is called without supplying the ID namely called as

ProjectName/Controller/index

it will return an error as it expects a parameter. Is there a way to check if a parameter exists.

Answer 1

No there is not a way to check if one exists per-say as that error happens before the controller has a chance to run code. ie. before the class method executes.

That said there is a simple workaround for this: You can supply a default value and check for that for example

function index($id = null){
     if( is_null($id) ){
          ///do something - like show a pretty error, or redirect etc...
     }else{
        $this->model->get_user($id);
     }
}

This way when no parameter is supplied the ID will be null, this is fairly safe ( when using null ) because you can never supply null as part of the url path even doing this

   www.mysite.com/index/null  //or however the url works out in your case

Will supply null as a string, because everything in the url comes through as a string. So 'null' as a string is not in fact null it's just the word null. If that makes sense. So given that null could never be supplied and only happens if no other value is supplied.

In this case it may be worth casting the input to a int or further checking if it's an improper value.

This could be done several ways:

Casting:

  function index($id = null){
     if( is_null($id) ){
          ///do something - like show a pretty error, or redirect etc...
     }else{
        $this->model->get_user((int)$id);
        //cast to int, things that are not INT or string equivalents become 0, which should not find a user as it would look for ID = 0
     }
}

By Regx check:

function index($id = null){
     if( is_null($id) ){
          ///do something - like show a pretty error, or redirect etc...
    }else if( preg_match('/^[^\d]+$/', $id )){
         // not an int ( contains anything other than a digit )
    }else{
        $this->model->get_user($id);
     }
}

Cheers.