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How do I make a column unique and index it in a Ruby on Rails migration?
...ld versions of Rails (see other answers for Rails 4+):
add_index :table_name, :column_name, unique: true
To index multiple columns together, you pass an array of column names instead of a single column name,
add_index :table_name, [:column_name_a, :column_name_b], unique: true
If you get "inde...
Converting an int to std::string
...e, to convert an int to a string? Answers using stl and boost will be welcomed.
11 Answers
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Return first N key:value pairs from dict
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There's no such thing a the "first n" keys because a dict doesn't remember which keys were inserted first.
You can get any n key-value pairs though:
n_items = take(n, d.iteritems())
This uses the implementation of take from the itertools recipes:
from itertools import islice
def take(n,...
Unable to create/open lock file: /data/mongod.lock errno:13 Permission denied
...use a mounted drive on ec2? I really do not understand. I attached a volume on ec2 formatted the drive as root and start as root and yet as root I cant access? I am running on ubuntu 12.04. No other mongo is running
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Search all the occurrences of a string in the entire project in Android Studio
...this IDEA has a nice "Find Usages" command. It can be found in the context menu, when the cursor is on some field, method, etc.
It's context-aware, and as far as I know, is the best way to find class, method or field usage.
Alternatively, you can use the
Edit > Find > Find in path…
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How to find index of all occurrences of element in array?
I am trying to find the index of all the instances of an element, say, "Nano", in a JavaScript array.
15 Answers
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How do you convert a time.struct_time object into a datetime object?
How do you convert a Python time.struct_time object into a datetime.datetime object?
3 Answers
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Detecting if an NSString contains…?
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Here's how I would do it:
NSString *someString = @"Here is my string";
NSRange isRange = [someString rangeOfString:@"is " options:NSCaseInsensitiveSearch];
if(isRange.location == 0) {
//found it...
} else {
NSRange isSpacedRange = [someString rangeOfString:...
How do you underline a text in Android XML?
...; </i> and <u> </u>.
<resources>
<string name="your_string_here">
This is an <u>underline</u>.
</string>
</resources>
If you want to underline something from code use:
TextView tv = (TextView) view.findViewById(R.id.tv);
Spann...
Apply CSS Style to child elements
..., td, caption {padding:40px 100px 40px 50px;}" applies a rule to all th elements which are contained by a div element with a class named test, in addition to all td elements and all caption elements.
It is not the same as "all td, th and caption elements which are contained by a div element with a ...