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When one wishes to convert a list to a vector or data.frame object empty elements are typically dropped. This can be problematic which a list is created of a desired length are created with some empty values (e.g. a list with n elements is created to be added to an m x n matrix, data.frame, or data...

user_one = User.find(1) user_two = User.find(1) user_one.name = "John" user_one.save # Run at the same instance user_two.name = "Doe" user_two.save # Raises a ActiveRecord::StaleObjectError

appointment = Appointment.find(5) appointment.lock! #no other users can read this appointment, #they have to wait until the lock is released appointment.save! #lock is released, other users can read this account

If you want to use RSpec for a Rails project, you should use the rspec-rails gem, which can generate helpers and spec files for you automatically (for example, when you create models, resources or scaffolds using rails generate). Add rspec-rails to both the :development and :test groups in the Gem...

This is a copy of the advanced function snippet from the Powershell ISE. Basically this is a template for many of the things you can use with advanced functions in Powershell. Key points to note: get-help integration - the beginning of the function contains a comment block that is set up to be ...

To work with ConstraintLayout, you need Android Studio Version 2.2 or newer and have at least version 32 (or higher) of Android Support Repository. Add the Constraint Layout library as a dependency in your build.gradle file: dependencies { compile 'com.android.support.constraint:constraint...

Define your payload to send for possible more complex data $Payload = @{ text="test string"; username="testuser" } Use ConvertTo-Json cmdlet and Invoke-RestMethod to execute the call Invoke-RestMethod -Uri "https://hooks.slack.com/services/yourwebhookstring" -Metho...

SELECT department, COUNT(*) AS "Man_Power" FROM employees GROUP BY department;

SELECT department, COUNT(*) AS "Man_Power" FROM employees GROUP BY department HAVING COUNT(*) >= 10; Using GROUP BY ... HAVING to filter aggregate records is analogous to using SELECT ... WHERE to filter individual records. You could also say HAVING Man_Power >= 10 since HAVIN...

1. Print the Hadoop version hadoop version 2. List the contents of the root directory in HDFS hadoop fs -ls / 3. Report the amount of space used and available on currently mounted filesystem hadoop fs -df hdfs:/ 4. Count the number of directories,files and bytes under the paths tha...

For enabling Proguard configurations for your application you need to enable it in your module-level gradle file. You need to set the value of minifyEnabled to true. buildTypes { release { minifyEnabled true proguardFiles getDefaultProguardFile('proguard-android.t...

Example of calling an extension method as an extension and as a regular method. public Class MyClass Sub Main() 'Extension called directly on the object. Dim Version = Assembly.GetExecutingAssembly.GetVersionFromAssembly() 'Called as a regular method. ...

main.component.ts import {Component} from "@angular/core"; @Component({ selector: "main", template: ` <StackLayout> <TextField hint="some text"></TextField> <Button text="Click me" class="btn">...

Create a Dictionary<TKey, TValue> from an IEnumerable<T>: using System; using System.Collections.Generic; using System.Linq; public class Fruits { public int Id { get; set; } public string Name { get; set; } } var fruits = new[] { new Fruits { Id = 8 , Nam...

There are times when an include file has to generate different output from the preprocessor depending on whether the compiler is a C compiler or a C++ compiler due to language differences. For example a function or other external is defined in a C source file but is used in a C++ source file. Since...

A common problem in code that uses multidimensional arrays, arrays of pointers, etc. is the fact that Type** and Type[M][N] are fundamentally different types: #include <stdio.h> void print_strings(char **strings, size_t n) { size_t i; for (i = 0; i < n; i++) puts(str...

When allocating multidimensional arrays with malloc, calloc, and realloc, a common pattern is to allocate the inner arrays with multiple calls (even if the call only appears once, it may be in a loop): /* Could also be `int **` with malloc used to allocate outer array. */ int *array[4]; int i; ...

So far, we have looked at inserting a node at the beginning of a singly linked list. However, most of the times you will want to be able to insert nodes elsewhere as well. The code written below shows how it is possible to write an insert() function to insert nodes anywhere in the linked lists. #...

There's no built in way to search a list for a particular item. However Programming in Lua shows how you might build a set that can help: function Set (list) local set = {} for _, l in ipairs(list) do set[l] = true end return set end Then you can put your list in the Set and test for m...

Objective-C UIColor *color = [UIColor redColor]; NSString *textToFind = @"redword"; NSMutableAttributedString *attrsString = [[NSMutableAttributedString alloc] initWithAttributedString:yourLabel.attributedText]; // search for word occurrence NSRange range = [yourLabel.text rangeO...