Salient Soft

Whilst Angular 2 routing is handled via routers, Ionic takes a different approach with the use of the NavController and related components based on it like Nav and Tab.

Ionic navigation allows views to be pushed and popped from a navigation stack, and allows a root page to be established for a particular navigation stack.

A useful tutorial on Ionic Navigation may be found here.

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There is no specific feature for doing this in Fauxton – you can upload attachments but not specifically delete them.

You can delete the attachment programmatically by issuing an HTTP DELETE to the attachment’s URL

This post here states that removing the stub reference to the attachment in “_attachments” in the document actually does the same as deleting programmatically as above.

In both cases, the stub is deleted, and the actual attachment is marked for delete. It will only actually be deleted when the database is compacted. However, the important point is that both methods apparently do the same thing.

Therefore, in Fauxton, you can just edit the JSON for the document to remove the attachment stub, and save the change.

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An <ion-item> is used (among other things) as the child of an ion-list and has a number of options, detailed here.

A particular issue I hit was that by default text in an item is truncated with an ellipsis on the end, whereas I wanted it to wrap and grow the item height.

Points on this:-

1. The item is set to have a min-height and so is capable of expanding down.
2. By default, it is set to have white-space:nowrap which prevents wrapping, and text-overflow:ellipsis which gives the ellipsis.
3. Wrap can be enabled per the text alignment section in the above ion-item page, using a utility attribute documented here. These attributes are useful as they allow general types of text transformation on a variety of components. In this case, adding the text-wrap attribute to the ion-item allows the text to wrap – it triggers a css attribute selector to set white-space:wrap (a neat use of custom attributes on a custom tag to trigger a css style rule directly).
4. Note that the container for the ion-item and its various parent containers are all set to overflow:hidden, but this does not prevent text wrapping when white-space:wrap is in effect as above.

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It is useful to enable CORS when using CouchDB for development, as this avoids the need for workarounds such as installing e.g. the CORS plugin in Chrome to bypass CORS issues.

As CORS is enabled/allowed on the Server Side, this needs to be enabled in CouchDB. This post details approaches to this. The easiest way (which is mentioned in the post comments) is just to do it in Fauxton. Just pick configuration on the left, and select CORS. You can enable for all domains (simplest for a closed development environment) or create a list. This github commit here can also do it but appears long winded compared to just doing it in Fauxton for simple cases.

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Sometimes you need an element to hang e.g. an *ngIf directive on, but you don’t want the element to appear in the markup.

In the following example, we end up with an extra unwanted <div> level just because we needed to hang the *ngIf somewhere (noting that it is not permissible to have the *ngIf on the same element as the *ngFor).

<div *ngFor="let place of places.rows">
  <div *ngIf="place.doc.type == 'place'">
    <span>{{place.doc.name}}, </span>
    <span>{{place.doc.strapline}}</span>
  </div>
</div>

Instead of a <div> we can use <ng-container>. This does not appear as an element in the markup (but does appear as a comment only) :-

<div *ngFor="let place of places.rows">
  <ng-container *ngIf="place.doc.type == 'place'">
    <span>{{place.doc.name}}, </span>
    <span>{{place.doc.strapline}}</span>
  </ng-container>
</div>

This is analagous to the <th:block> dummy element in Thymeleaf, which does exactly the same thing.

This StackOverflow post details this issue. This alternative post mentions the use of ng-if-start and ng-if-end, but notes that these are undocumented in Angular 2 so may not be fully supported.

For a related issue where nested loops are in use causing a similar problem, this post details the use of ng-repeat-start and ng-repeat-end as an alternative solution.

Note however that ng-repeat-start/ng-repeat-end only works for Angular 1.

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During installation, I received the following error message:-

“The installer is unable to instantiate the file …{…}\KEY_XE.REG”

The installation was mostly correct but I was unable to access the getting started/home page.

This post here details a workaround for the issue but this did not  work for me.

In the end, I recreated the Get_Started.url file under (in my case) E:\oraclexe\app\oracle\product\11.2.0\server.

This contained a parameter placeholder for the HTTP port, and I just edited the correct port in directly. Note that for some reason it was not possible to change the existing shortcut. I had to delete it and create a new one of the same name, which then worked fine.

Whilst doing this, I also changed the HTTP port that the web interface listens on. This is done by running a stored procedure, and is detailed in both this post and also this alternative post. Both posts detail the same method.

Note also for XE 11g R2 that the getting started page (which corresponds to the old 10g home page) no longer has the means to create schemas or to run sql queries. Schemas/users can be created via SQLplus, or via TOAD or SQLDeveloper.

Note that TOAD 8 is not compatible with 11g. The latest free TOAD now lasts for a year and is excellent with plenty of functionality, albeit with an occasional nag/advert for the paid version. The paid version is around $800 for a seat which is very high for a SQL development tool, even if it is a good one. Note that the free TOAD is available from Toad World here, but is not available from the main Quest Software site – this appears to be a marketing decision to keep the free version out of sight from people who may be persuaded to part with money for the paid one. I should not complain too much as they are after all providing an excellent free tool.

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Update 15/5/2012

Further to the issues below, whilst I could run Sage satisfactorily for the most part, some features still needed ODBC to be working, such as Invoice preview and VAT return printing.

After a couple of attempts I was able to setup ODBC after the event by running E:\Salient Soft\Accounts\Sage\Instant Accounts\ODBC32\Disk1\Setup.exe. This allowed ODBC setup/install even after Sage had been installed.

Sage was happy even though there was no mention of the ODBC driver or connection for Sage under Administrative Tools/Data Sources (ODBC). The real underlying issue was not discovered, but the problem was finally resolved.

I was then able to successfully print a VAT return and preview invoices, which previously had failed.

Original Post

This was a reinstall using a fresh windows install, but the same location for Sage on a data disk. The following issues were hit:-

1. On install, it hung at the point where it said “Setup is configuring the ODBC”
2. I tried installing from a shortcut to the CD, with administrator mode set and Windows XP compatibility of various flavours, but the same error persisted.
3. I then tried removing the “ODBC files” option from the (custom) install. This changed the problem – the install now hung at the point where it said “configuring MIS files”.
4. I then did another custom install removing everything that I did not need, including ODBC, MIS support, E-Banking, web/email templates etc.
5. This time, the install finished successfully. Furthermore, Sage ran fine even though I had not told it to “configure the ODBC”.

Note that it is possible that the previous duff installs did configure ODBC and that the final install was dependant on the previous ones to work. This should be borne in mind if trying again. However, all the installed files for Sage were all there anyway as this was a reinstall – I was only doing it to install the windows/registry settings/shortcuts etc. that Sage needed.

I did not try a new install to a new directory as I did not need to – this may have worked, but I cannot say. If so, it may be possible to import or copy the old company data into a new install. A quick look at the menus and a quick google did not reveal any obvious way to do this, but a judicios copy may work.

Note also that this issue did not occur the first time I installed on Windows 7 64. This first time was also an install over an existing Sage installation copied from Windows XP.

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I received this error whilst performing a commit via Eclipse:-

The server reported an error while performing the "cvs add" command. cvs server: xxx added independently by second party

The error related to some test database scripts in the project. I searched for solutions to this, and found some comments about tagging the files as merged, but this was not really any help.

In the end, I examined the files using TortoiseCVS, and noted that the offending files were not flagged as being under source control – they did not have any icon decoration on them.

In the end the following steps solved the problem:-

1. I made sure I had copies of them elsewhere, and then deleted them from the (TortoiseCVS managed) directory under the eclipse project.
2. I then did an Update with TortoiseCVS – this reloaded the latest versions from CVS, and this time they were correctly icon-decorated as managed.
3. I then copied the new versions in to replace these. When I did this, the new versions were correctly decorated in red as updated versions but known to CVS/Tortoise.
4. I then did a commit with Eclipse, and this now proceeded without error.
5. Finally to be safe, I did a file compare to check that the correct latest versions were in place.

This solved the problem. It appeared that somehow I had lost the required CVS metadata such that the files did not appear to be CVS managed. Tortoise was very helpful here – if you see files with no icon decoration, this is immediately suspicious.

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Update 7/12/22

Previously I have implemented a composite iterator for iterating a tree of tags from a search on a PropertyTree implementation. Note that in this case, the abstract base class for the composites was a TagTree, and the concrete subclasses were a TagList and a Tag. As a Tag did not need a list, the list of children was in the concrete TagList and not the TagTree. Therefore, the TagTree did not need to have generic references to self referential subtypes in the way the example below does – in fact it did not need to be generic at all. Therefore it did not suffer this problem. For further clarity see the example below from Angelika Langer here. In her code, the list is in the abstract superclass which is why it suffers the problem below and potentially needs the infamous getThis trick per below.

Original Post

Some generic classes are recursively self-referential, such as in the following abstract class statement for a tree node :-

public abstract class Node <N extends Node<N>>  {
…
}

In this situation it is sometimes necessary for example to pass a reference to this from the superclass to a specific subclass which expects an argument of type N :-

public void methodA(N node) {
//do something with the passed node
}

public void methodB(N node) {
node.methodA(this); // error – incompatible types
}

In the above fragment, the error is because this in the superclass has a type of Node<N> which does not match N.

Another related use case is where a fluent API returns a ‘this’ reference from each of the fluent methods. If for example a fluent method in an abstract base class needs to return a ‘this’, as above the reference needs to be for the concrete subclass so the same problem occurs.

The topic is discussed in detail in Java Generics and Collections, section 9.4 on the Strategy pattern. The section from the book may be viewed online at Flylib here.

Angelika Langer also discusses it in more detail her Generics FAQ here

In the above case, the problem can be solved with the so-called getThis trick. An abstract getThis method is defined in the superclass, and implemented in each subclass:-

Superclass

protected abstract N getThis();

Subclass

protected Subtype getThis() {return this}; // where Subtype is the concrete subtype of N

Now the superclass can obtain a type correct reference to this and pass it without error:-

public void methodB(N node) {
node.methodA(getThis()); // this time it works
}

As Angelika Langer points out in her examples, there can be other ways around this kind of problem depending on the situation, but sometimes you do need the getThis trick.

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When a service layer EJB method is called locally from within the same class, any CDI interceptors on the method are not invoked. This is standard CDI behaviour, as interceptors are only designed to be called when a method is called from an external client.

I hit this issue when my OptimisticLockInterceptor (which converts OptimisticLockException to ChangeCollisionException) was not being called, and OptimisticLockExceptions where being propagated all the way up to the view layer -  Mantis issue 120 details this.

The solution to this is to ensure that any required interceptors are annotated on methods at the point of call from an external client. If they then call another EJB method locally, any interceptors on the second method will not be called, but this is not a problem if the first method is correctly annotated. If the second method is also used externally, then its interceptors will be correctly invoked.

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