I have need of this several times and I haven't come with a good solution
neither have found one.
Split a full node name like the one returned by
node()
which is in the form
FullName = 'node_name#localhost'
and I want to split in the node name, hostname
{ 'node_name', 'localhost'} = split_node_name(FullName)
So far I have converted to list and split on the #, but
It feels ugly and something should be in the standard lib.
string:tokens works like split() in other languages.
A = atom_to_list(node()).
string:tokens(A, "#").
In your case, it will return ['node_name', 'localhost'].
If you want it to a tuple, use list_to_tuple()/1
list_to_tuple(A).
I came up with somtehing like this:
list_to_tuple([list_to_atom(A)||A<-string:tokens(atom_to_list(node()), "#")]).
Related
In Java, the string search by its' substring goes like this:
String string = "Madam, I am Adam";
b = string.matches("(?i).*i am.*");
How to find an instance in Grails by name where query is any part of its name?
I think this is what you're looking for
DomainClass.findByNameIlike("%i am%")
That is a case insensitive search for any record with name containing "I am". This is not an efficient way to query a database, so if your application will experience any kind of load, you should use it sparingly.
Edit: Documentation
I'm writing an MVC application and want to query my database with a search parameter and put all of the results into a list. Right now my code to try this looks like:
Character character = db.Characters.ToList().Find(User.Identity.GetUserId());
Which is throwing up a error. Is there a way I can do this? Break it down into two statements for example? I tried
Character character = db.Characters.Find(User.Identity.GetUserId());
character = character.ToList();
but that isn't working either.
When using the extension method Find() you must be sure that in your model you have the attribute [Key] in the property representing your Id (primary key in your table).
And you can try like this:
Character character = db.Characters.Find(User.Identity.GetUserId());
The line above will work but not this one character= character.ToList(); because you declare character as an object and you can't assign it to a list of object in your case Character
If you want it to work, you can do something like this:
var myCharacters =db.Characters.Where(c=>c.someField=="someValue");
List<Character> myList = myCharacters.ToList();
Hope it will help.
I have been using parameters to query node indexes as such (using the rest api in java)-
final QueryResult<Map<String,Object>> result = engine.query("start nd=node:name_index(name={src}) return nd.age as age", MapUtil.map("src", "Susan");
However I haven't been able to get this to work for a collection of nodes/names. I have been trying something along the lines of-
final QueryResult<Map<String,Object>> result = engine.query("start nd=node:name_index(name={src}) return nd.age as age", MapUtil.map("src", Arrays.asList("Susan","Brian", "Ian"));
But it refuses to compile. I as wondering if there is something wrong in my syntax or that parameters are not designed to work in this context.
The name= syntax in the start is meant to do an index lookup on a property. It won't do an IN lookup. The way you can do this sort of lookup is like this (note it depends on Apache's StringUtils):
List<String> names = Arrays.asList("Susan","Brian", "Ian");
String luceneQuery = "name:("+StringUtils.join(names, ",")+")";
engine.query("start nd=node:name_index({luceneQuery}) return nd.age as age", MapUtil.map("luceneQuery", luceneQuery));
Just a note, this is the "legacy" index way of doing things. In 2.0 they've introduced label-based indexes, which work entirely differently.
Thanks a lot; though it would still only return a non empty answer when I added a space after the comma in line 2. I used-
String luceneQuery = "name:("+StringUtils.join(names, ", ")+")";
and it returned the age of one person. When I tried this:
String luceneQuery = "fs:(fs:"+ StringUtils.join(names, " OR fs:")+")";
it gave me all three ages. However, I am still unsure about whether this query will be able to leverage the usual advantages of parameters , i.e. will the engine be able to reuse the query and execution path the next time around (this time we may want to query for 4 names instead of 3)
I have the following lambda for a simple search page using MVC:
Name and PostedName are strings.
Results.where(a=>a.Name.Contains(PostedName)).ToList();
Thanks great when PostedName has a value (excellent filter), but when it is empty, I get bupkas (empty list).
I would ideally like my where clause to be ignored when empty string.
How can this be done?
Something ideally shorthand without ifs and elses and whatifs.
Thanks!
You can dynamically add the WHERE clause. Keep in mind that you're just building an expression tree with these clauses and it's not actually executed until, in this case, you call .ToList(). So you can do something like this:
var filteredResults = Results;
if (!string.IsNullOrWhitespace(PostedName))
filteredResults = filteredResults.Where(a => a.Contains(PostedName));
filteredResults = filteredResults.ToList();
Depending on the types you may need to explicitly declare a type for filteredResults in order for that to compile.
If you want something a little more in-line, this may do the trick:
Results.Where(a => string.IsNullOrWhitespace(PostedName) || a.Contains(PostedName)).ToList();
I think it's less clear on the intent, though. The benefit of the first example is also that you can add more filters following the same structure, basically dynamically adding more WHERE clauses for other filter fields as needed.
David's answer is correct, but if you want a shortcut you can create an extension method to simplify usage example (untested by me).
I would suggest:
Results.Where(a => a.Name.Contains((PostedName ?? "").Trim())).ToList();
"ThisIsAString".Contains("") returns true.
In the case PostedName is null, it will be changed to "".
If there is leading and/or trailing blanks characters in PostedName, then they will be removed.
Assume the following:
class Thing {
String name
List<String> tags
static constraints = {
name(nullable: false)
tags(nullable: false)
}
}
I want to know if its possible, using GORM, to run a query for domain instances based on values in their respective lists
For instance: Are there dynamic GORM finders to query things like 'Find all Things that have the tag "Video" ', or 'Find all things with name = "Product1" that have the tag "Image" '
Just want to know if there's a nice concise way of doing this with Grails&Gorm, as opposed to retrieving a list of Things and iterating through it, finding the ones that have the appropriate tags and adding them to a results list.
Thanks!
One way (although not necessarily the most efficient!) would be to return the whole list of Things eg Thing.list() and then filter the resulting list using findAll.
List results = Thing.list().findAll{it.tags.contains("Image")}
How big is your list of Things and associated Tags likely to be?