Categories
discuss

Is there a better jQuery solution to this.form.submit();?

I want to trigger the submit event of the form the current element is in. A method I know works sometimes is:

this.form.submit();

I’m wondering if there is a better solution, possibly using jQuery, as I’m not 100% sure method works in every browser.

Edit:

The situation I have is, as follows:

<form method="get">
    <p><label>Field Label
        <select onchange="this.form.submit();">
            <option value="blah">Blah</option>
            ....
        </select></label>
    </p>
</form>

I want to be able to submit the form on change of the <select>.

What I’m looking for is a solution that works on any field within any form without knowing the id or name on the form. $('form:first') and $('form') won’t work because the form could be the third on the page. Also, I am using jQuery on the site already, so using a bit of jQuery is not a big deal.

So, is there a way to have jQuery retrieve the form the input/select/textarea is in?

Answer

I think what you are looking for is something like this:

$(field).closest("form").submit();

For example, to handle the onchange event, you would have this:

$(select your fields here).change(function() {
    $(this).closest("form").submit();
});

If, for some reason you aren’t using jQuery 1.3 or above, you can call parents instead of closest.

Categories
discuss

Is Google Web Toolkit useful to develop complex javascripts?

Iam a great fan of javascript frameworks especially jQuery .I have always wanted to design sites like “plurk.com” but i know that it needs very huge lines of javascript.so that shut me off.But since i came to know GWT , i really want to test it out and want to ask you if it makes our job easier to develop complex things than with the javascript or its frameworks .Which one would you prefer ?

Answer

Few things scare me like “generated Javascript”. The Law of Leaky Abstractions has got to be doubly true in these cases.

Writing effective cross-browser javascript is a tricky process of continuous refinement. Trying to decipher where some generated, obscured Javascript is going wrong is a major headache. It’s bad enough fixing bugs in the pure JS libraries.

To me, GWT is a trick aimed at allowing backend developers to write front-end, in-browser code. Unfortunately, the realities of modern web apps mean you just have to know Javascript and the DOM. Something’s going to break, and you’re going to need to know why.

I think you’re better off picking a good javascript library like jquery or prototype, and learning that well. Those libraries abstract away the sort of stuff that SHOULD be abstracted away and is unlikely to break in edge cases, like array operations and AJAX requests.

Categories
discuss

Java map with values limited by key’s type parameter

Is there a way in Java to have a map where the type parameter of a value is tied to the type parameter of a key? What I want to write is something like the following:

public class Foo {
    // This declaration won't compile - what should it be?
    private static Map<Class<T>, T> defaultValues;

    // These two methods are just fine
    public static <T> void setDefaultValue(Class<T> clazz, T value) {
        defaultValues.put(clazz, value);
    }

    public static <T> T getDefaultValue(Class<T> clazz) {
        return defaultValues.get(clazz);
    }
}

That is, I can store any default value against a Class object, provided the value’s type matches that of the Class object. I don’t see why this shouldn’t be allowed since I can ensure when setting/getting values that the types are correct.

EDIT: Thanks to cletus for his answer. I don’t actually need the type parameters on the map itself since I can ensure consistency in the methods which get/set values, even if it means using some slightly ugly casts.

Answer

You’re not trying to implement Joshua Bloch’s typesafe hetereogeneous container pattern are you? Basically:

public class Favorites {
  private Map<Class<?>, Object> favorites =
    new HashMap<Class<?>, Object>();

  public <T> void setFavorite(Class<T> klass, T thing) {
    favorites.put(klass, thing);
  }

  public <T> T getFavorite(Class<T> klass) {
    return klass.cast(favorites.get(klass));
  }

  public static void main(String[] args) {
    Favorites f = new Favorites();
    f.setFavorite(String.class, "Java");
    f.setFavorite(Integer.class, 0xcafebabe);
    String s = f.getFavorite(String.class);
    int i = f.getFavorite(Integer.class);
  }
}

From Effective Java (2nd edition) and this presentation.

Categories
discuss

Java Interfaces? [closed]

I really need help with interfaces in general…

Any resources that you guys would recommend me?

Related:

Answer

What is an Interface? from Java’s official tutorial

Edit: A second resource from the same tutorial, is the Interfaces and Inheritence section.

Categories
discuss

JPA map collection of Enums

Is there a way in JPA to map a collection of Enums within the Entity class? Or the only solution is to wrap Enum with another domain class and use it to map the collection?

@Entity
public class Person {
    public enum InterestsEnum {Books, Sport, etc...  }
    //@???
    Collection<InterestsEnum> interests;
}

I am using Hibernate JPA implementation, but of course would prefer implementation agnostic solution.

Answer

using Hibernate you can do

@CollectionOfElements(targetElement = InterestsEnum.class)
@JoinTable(name = "tblInterests", joinColumns = @JoinColumn(name = "personID"))
@Column(name = "interest", nullable = false)
@Enumerated(EnumType.STRING)
Collection<InterestsEnum> interests;
Source: stackoverflow
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Privacy Policy, and Copyright Policy. Content is available under CC BY-SA 3.0 unless otherwise noted. The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 © No Copyrights, All Questions are retrived from public domain..