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mongoDB/mongoose: unique if not null
...ngoDB v1.8+ you can get the desired behavior of ensuring unique values but allowing multiple docs without the field by setting the sparse option to true when defining the index. As in:
email : {type: String, trim: true, index: true, unique: true, sparse: true}
Or in the shell:
db.users.ensureIn...
Add Bootstrap Glyphicon to Input Box
...in Plunker
Note: This presumes you're using glyphicons, but works equally well with font-awesome.
For FA, just replace .glyphicon with .fa
With Bootstrap:
As buffer points out, this can be accomplished natively within Bootstrap by using Validation States with Optional Icons. This is do...
What is a Manifest in Scala and when do you need it?
Since Scala 2.7.2 there is something called Manifest which is a workaround for Java's type erasure. But how does Manifest work exactly and why / when do you need to use it?
...
How to create a density plot in matplotlib?
...with R. This is because gaussian_kde tries to infer the bandwidth automatically. You can play with the bandwidth in a way by changing the function covariance_factor of the gaussian_kde class. First, here is what you get without changing that function:
However, if I use the following code:
import...
What is the difference between Pan and Swipe in iOS?
...esture is continuous. It begins (began) when the minimum number of fingers allowed (minimumNumberOfTouches) has moved enough to be considered a pan. It changes (changed) when a finger moves while at least the minimum number of fingers are pressed down. It ends (ended) when all fingers are lifted.
C...
Android static object lifecycle
...cation?
The OS starts a process and assigns it a unique process id and allocates a process table.A process start an instance of DVM(Dalvik VM); Each application runs inside a DVM.
A DVM manages class loading unloading, instance lifecycle, GC etc.
Lifetime of a static variable: A static variable...
Custom attributes in styles.xml
...ither. If you don't have the custom namespace xmlns attribute, you can actually type in any value you like for the item name attribute and it will compile.
– David Snabel-Caunt
Dec 19 '11 at 8:56
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Preferred Github workflow for updating a pull request after code review
...pull request and push the branch to GitHub. The pull request will automatically be updated with the additional commit.
#2 and #3 are unnecessary. If people want to see only where your branch was merged in (and not the additional commits), they can use git log --first-parent to only view the merge c...
What is the purpose of the “Prefer 32-bit” setting in Visual Studio and how does it actually work?
...
Microsoft has a blog entry What AnyCPU Really Means As Of .NET 4.5 and Visual Studio 11:
In .NET 4.5 and Visual Studio 11 the cheese has been moved. The
default for most .NET projects is again AnyCPU, but there is more than
one meaning to AnyCPU now. There i...
Performant Entity Serialization: BSON vs MessagePack (vs JSON)
...k is designed to be transparently converted from/to JSON.
MessagePack is smaller than BSON
MessagePack's format is less verbose than BSON. As the result, MessagePack can serialize objects smaller than BSON.
For example, a simple map {"a":1, "b":2} is serialized in 7 bytes with MessagePack, while B...