I beat myself up for two days as I built a Ruby on Rails application that manages users in LDAP. While fine-tuning the inclusion and formatting of various attributes, I would frequently have ldap.add() fail with little feedback other than possibly an exception raised. I usually knew it was a data validation error, such as a missing required attribute or poorly formatted attribute values -- but I could not find anything on the server (Apache DS) or client end that would indicate which field failed, or why it was failing.
So...how do you see the reason why an LDAP add (or replace, delete, open...) failed?
Then I stumbled across ldap.get_operation_result, I had a real facepalm moment. I've intentionally recreated several of the issues I painfully solved through careful inspection with get_operation_result in my arsenal, and each time it described exactly what the problem was.
This function is useful in the case of rescuing an exception, or if add(), modify(), delete(), etc. simply returns false.
ldap.add(dn: dn, attributes: attributes)
Rails.logger.info("ldap.add: #{ldap.get_operation_result}")
The snippet above saved my sanity, not to mention hours of tedious hunt-and-peck testing.
For example, here is just one part of an error message it revealed that I did not provide the required sn attribute:
ERR_279 Required attributes [sn(2.5.4.4)] not found within entry uid=david,o=users,dc=example,dc=com"
It will also show messages related to bad server connection credentials, etc.
HTH
I would like to display some info on the screen ... which will disappear.
Example : an Uiview is displayed for the first time to an user (or feature never used by the user). I would like to display on a screen a label or an image to explain how to use this new feature. After that it will disappear ...
If this functionality has already been used by the user, the message is ofcourse not displayed.
example of message --> to add a gamer, press +
How to do that ? a lot of apps have this kind of help.
thanks
What you have to do is actually very simple : have a persistent variable, and change its value. Each time the user could see the help popup, you check the value of the variable you stored persistently. If this variable indicates that the user have already seen the help, you don't display it again. Otherwise, you show it. Simple example:
let helpSeen: Bool = getVarFromPersistent()
if helpSeen == false {
// DISPLAY THE HELP MESSAGE OR POPUP
setHelpSeenVar(true)
}
Where getVarFromPersistent() and setHelpSeenVar() are function you could create to respectively retrieve the variable from the persistent data and set the variable in the persistent data.
Now, you have to figure out how to use persistent data. You can have a look at CoreData, that is provided by Apple and "ready to use" in Xcode. You've probably already seen the use core data tickbox when you create a project.
Third party libraries exists as well like RealmSwift, who reached version 1.0 recently.
I'm not an expert, but I think Realm is simpler to use than Core Data. The technology used by the two libraries could be different though, maybe someone else could tell you more about it. Anyway, you will find a lot of article about Realm and Core Data on Google.
I'm working on a simple CRUD proof of concept with Rails/Backbone/JST templating. I've been able to find a lot of examples up to this point. But after much searching and reading, I've yet to find a good example of how to handle these scenarios:
info message: new item successfully added to list (shown on list screen)
info message: item successfully deleted from list
error message: problem with field(s) entry
field level error message: problem with entry
The Backbone objects are:
Collection (of "post" Models) -> Model ("post" object) -> List/Edit/New Views (and a JST template for each of these views)
So, I'm looking for a high level description of how I should organize my code and templates to achieve the level of messaging desired. I already have a handle on how to perform my validation routine on the form inputs whenever they change. But not sure what do with the error messages now that I have them.
Here is the approach I'm considering. Not sure if it's a good one:
Create a "Message" Model, which maps to a "View", which is a sub-view (if that's possible) on my existing views. This view/model can display page level messages and errors in the first three scenarios I mention above. Not sure if it's feasible to have a "sub-view" and how to handle the templating for that. But if it's possible, the parent templates could include the "message" sub-template. The message view could show/hide the sub-template based on the state of the message model. Feasible? Stupid?
For the fourth scenario, the model validation will return an error object with specific messages per each erroneous field each time a "model.set" is called by form field changes. I don't want to interrupt the "model.set" but I do want to display the error message(s) next to each field. I want to know how to factor my edit/new template and Post model/view in such a way that I don't violate the MVC pattern. I.e. I don't want to put references to DOM elements in the wrong plage.
Sorry if this is vague. If you're inclined to help, let me know what code snippets could be helpful (or other details) and I'll provide them.
You create a global eventbus. When ever an error appears trigger an event. Your view that should show the message listen to the events on this eventbus. Doing so, your error message view dont needs to know all of your collection and vice versa. The eventbus is simple:
var eventBus = _.extend({}, Backbone.Events);
Add it to your collection and trigger it when ever add was called:
var myCollection = Backbone.Collection.extend({
initialize: function([],eventbus){
this.bind('add', function(obj){eventbus.trigger('added', obj)}
}
})
Take also a look at the article: http://lostechies.com/derickbailey/2011/07/19/references-routing-and-the-event-aggregator-coordinating-views-in-backbone-js/
I am rather new to mvc2 and when following a writeup on data annotations and such, I came across a bit of code that let me manually add a line of text to the validation summary.
I've searched for the last 2 or 3 hours and I've come to the point where I think I'm just searching for the wrong thing. Its not custom validators I'm looking for, but something that I can call from the controller to add error messages.
Does anyone know what I'm talking about?
edit: clarified title a bit
Are you looking for:
ModelState.AddModelError("*", "There was an error processing your request")
MSDN - ModelStateDictionary.AddModelError Method (String, String)
MSDN - Validating Model Data in an MVC Application
HTHs,
Charles
Suppose you have a subsystem that does some kind of work. It could be anything. Obviously, at the entry point(s) to this subsystem there will be certain restrictions on the input. Suppose this subsystem is primarily called by a GUI. The subsystem needs to check all the input it recieves to make sure it's valid. We wouldn't want to FireTheMissles() if there was invalid input. The UI is also interested in the validation though, because it needs to report what went wrong. Maybe the user forgot to specify a target or targetted the missles at the launchpad itself. Of course, you can just return a null value or throw an exception, but that doesn't tell the user SPECIFICALLY what went wrong (unless, of course, you write a separate exception class for each error, which I'm fine with if that's the best practice).
Of course, even with exceptions, you have a problem. The user might want to know if input is valid BEFORE clicking the "Fire Missles!" button. You could write a separate validation function (of course IsValid() doesn't really help much because it doesn't tell you what went wrong), but then you'll be calling it from the button click handler and again from the FireTheMissles() function (I really don't know how this changed from a vague subsystem to a missle-firing program). Certainly, this isn't the end of the world, but it seems silly to call the same validation function twice in a row without anything having changed, especially if this validation function requires, say, computing the hash of a 1gb file.
If the preconditions of the function are clear, the GUI can do its own input validation, but then we're just duplicating the input validation logic, and a change in one might not be reflected in the other. Sure, we may add a check to the GUI to make sure the missle target is not within an allied nation, but then if we forget to copy it to the FireTheMissles() routine, we'll accidentally blow up our allies when we switch to a console interface.
So, in short, how do you achieve the following:
Input validation that tells you not just that something went wrong, but what specifically went wrong.
The ability to run this input validation without calling the function which relies on it.
No double validation.
No duplicate code.
Also, and I just thought of this, but error messages should not be written in the FireTheMissles() method. The GUI is responsible for picking appropriate error messages, not the code the GUI is calling.
"The subsystem needs to check all the input it receives to make sure it's valid"
Think of the inputs not so much as a list of arguments, but as a message, it gets easier after that.
The message class has an IsValid member function, it remembers if IsValid was called and what the result was. It also remembers its state, if the state changes then it needs to be re validated. This message class also keeps a list of validation errors.
Now, the UI builds a TargetMissiles message, and the UI can validate it, or pass it directly to the MissileFiring subsystem, it checks to see if the message was validated, if not it validates it, and proceeds / fails depending.
The UI gets the message back, with the list of validations already populated.
The messages with their validation sit in a separate library. No code is duplicated.
This sound OK?
This is what Model-View-Controller is all about.
You build up a model (a launch which is composed of coordinates, missile types and number of missiles) and the model has a validate method which returns a list of errors/warnings. When you update the model (on key-up, <ENTER>, button-press) you call the validate method and show the user any warnings, errors, etc. (Eclipse has a little area just under the tools bar in a dialog that does this, you might want to look at that.)
When the model is valid, you activate the launch missiles button so that the user knows that they can launch the missiles. If you have an update event that is called particularly frequently or a part of the validation that is particularly costly, you can have a validate_light method on the model that you use for validating only the parts that are easy to do.
When you switch to a console based UI you build up the model from the command line arguments, call the same validate method (and report errors to stderr) and then launch the missiles.
Double the validation. In many case the validation is trebled (FKs and not null fields in the DB for example). Depending on your platform it may be possible to code the validation rules once. For example your front end and backend code could share C# business classes. Alternatively you could store the validation rule as metadata that both the backend and front end can access an apply.
In reality the fact that you need different responses to a validation problem (for example the Fire Missile button shouldn't even be enabled until the other inputs are valid) there will be different code associated with the same rule.
I'd suggest an input validation class, which takes the input type (an enumeration) in its' constructor, and provides a public IsValid method.
The IsValid method should return a boolean TRUE for valid and FALSE for invalid. It should also have an OUT parameter that takes a string and assigns a status message to that string. The caller will be free to ignore that message if it wants to, or report it up to the GUI if that's appropriate for the context.
So, in pseudocode (forgive the Delphi-like syntax, but it should be readable to anybody):
//different types of data we might want to validate
TValidationType = (vtMissileLaunchCodes, vtFirstName,
vtLastName, vtSSN);
TInputValidator = class
public
//call the constructor with the validation type
constructor Create(ValidationType: TValidationType);
//this should probably be ABSTRACT, implemented by descendants
//if you took that approach, then you'd have 1 descendant class
//for each validation type, instead of an enumeration
function IsValid(InputData: string; var msg: string): boolean;
And then to use it, you'd do something like this:
procedure ValidateForm;
var
validator: TInputValidator;
begin
validator := TInputValidator.Create(vtSSN);
if validator.IsValid(edtSSN.Text,labelErrorMsg.Text) then
SaveData; //it's valid, so save it!
//if it wasn't valid, then the error msg is in the GUI in "labelErrorMsg".
end;
Each piece of data has its own meta data (type, format, unit, mask, range etc.). Unfortunately this is not always specified.
The GUI controlls need to check the input with the metadata and give warnings/errors if the data is invalid.
Example: a number has a range. The range is provided by the metadata, but the range check is provided by the control.