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What is `params.require(:person).permit(:name, :age)` doing in Rails 4?
...rameter is present, and if it's not provided, the require method throws an error. It returns an instance of ActionController::Parameters for the key passed into require.
The permit method returns a copy of the parameters object, returning only the permitted keys and values. When creating a new Acti...
Sample random rows in dataframe
...ow make it better by checking first if n<=nrow(df) and stopping with an error.
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Correct way to detach from a container without stopping it
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it returns me: Error response from daemon: Container f560a0ad6806150b2775d0b6e6d5f7065a03775bae858fb4fb7df05a277976db is not running
– Webwoman
Mar 1 '19 at 13:27
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Is it better to call ToList() or ToArray() in LINQ queries?
...00.19.56404), X64 RyuJIT
| Method | Count | Mean | Error | StdDev | Median | Ratio | RatioSD | Gen 0 | Gen 1 | Gen 2 | Allocated |
|---------- |------ |--------------:|------------:|------------:|--------------:|------:|--------:|--------:|------:|------:|--...
How to add an auto-incrementing primary key to an existing table, in PostgreSQL?
...h this solution is that if the table already contains rows then you get an error: SQL Error [23502]: ERROR: column "id" contains null values
– isapir
Mar 7 '18 at 16:30
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Returning multiple values from a C++ function
... put the function definition of divide into a separate cpp file? I get the error error: use of ‘auto divide(int, int)’ before deduction of ‘auto’. How do I solve this?
– Adriaan
Feb 23 '18 at 20:26
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Android get free size of internal/external memory
...rmatSize(availableBlocks * blockSize);
} else {
return ERROR;
}
}
public static String getTotalExternalMemorySize() {
if (externalMemoryAvailable()) {
File path = Environment.getExternalStorageDirectory();
StatFs stat = new StatFs(...
How to iterate over arguments in a Bash script
I have a complex command that I'd like to make a shell/bash script of. I can write it in terms of $1 easily:
8 Answers
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Check if a variable is of function type
...rence (open your javascript console and reload page, there might be logged error messages). Note: Revision 3 added isFunctionD (based on only typeof == "function") - and it seems to be much faster than Underscore's "fast" version.
– Joel Purra
Feb 2 '12 at 18:3...
C++ lambda with captures as a function pointer
...code compiles fine without lambda captures, but there is a type conversion error with lambda capture.
Solution with C++11 is to use std::function (edit: another solution that doesn't require modifying the function signature is shown after this example). You can also use boost::function (which ac...