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Want to find records with no associated records in Rails
...).where( :friends => { :person_id => nil } )
For the hmt it's basically the same thing, you rely on the fact that a person with no friends will also have no contacts:
Person.includes(:contacts).where( :contacts => { :person_id => nil } )
Update
Got a question about has_one in the c...
What is the difference between std::array and std::vector? When do you use one over other? [duplicat
...ssic C array. That means its size is fixed at compile time and it will be allocated as a single chunk (e.g. taking space on the stack). The advantage it has is slightly better performance because there is no indirection between the object and the arrayed data.
std::vector is a small class contain...
How to convert a DOM node list to an array in Javascript?
...
Using spread (ES2015), it's as easy as: [...document.querySelectorAll('p')]
(optional: use Babel to transpile the above ES6 code to ES5 syntax)
Try it in your browser's console and see the magic:
for( links of [...document.links] )
console.log(links);
...
Why aren't variables declared in “try” in scope in “catch” or “finally”?
...Reader sr,
[1] class [mscorlib]System.Exception ex)
IL_0000: ldnull
IL_0001: stloc.0
.try
{
.try
{
IL_0002: ldsfld string UsingTest.Class1::path
IL_0007: newobj instance void [mscorlib]System.IO.StreamReader::.cto...
Get last result in interactive Python shell
...
Underscore.
>>> 5+5
10
>>> _
10
>>> _ + 5
15
>>> _
15
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Switching between GCC and Clang/LLVM using CMake
...xt with the following contents:
SET (CMAKE_C_FLAGS_INIT "-Wall -std=c99")
SET (CMAKE_C_FLAGS_DEBUG_INIT "-g")
SET (CMAKE_C_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
SET (CMAKE_C_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
SET (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
SET (...
Duplicate symbols for architecture x86_64 under Xcode
...at defines an Objective-C class or category. While this option will
typically result in a larger executable (due to additional object code
loaded into the application), it will allow the successful creation of
effective Objective-C static libraries that contain categories on
existing classes...
Pickle or json?
...ccf1b3fa91f4399902bb534/raw/03e8dbab11b5605bc572bc117c8ac34cfa959a70/pickle_vs_json.py
python pickle_vs_json.py
Results with python 2.7 on a decent 2015 Xeon processor:
Dir Entries Method Time Length
dump 10 JSON 0.017 1484510
load 10 JSON 0.375 -
dump 10 Pickle 0.011 ...
MySQL: What's the difference between float and double?
...00002 | 1.6900000000 |
This is using MySQL 6.7
Query:
SELECT
float_1 + float_2 as 'float add',
double_1 + double_2 as 'double add',
decimal_1 + decimal_2 as 'decimal add',
float_1 * float_2 as 'float multiply',
double_1 * double_2 as 'double multiply',
decimal_1 * decim...
From an array of objects, extract value of a property as array
...
Check out Lodash's _.pluck() function or Underscore's _.pluck() function. Both do exactly what you want in a single function call!
var result = _.pluck(objArray, 'foo');
Update: _.pluck() has been removed as of Lodash v4.0.0, in favour of _...