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Adding :default => true to boolean in existing Rails column
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change_column is a method of ActiveRecord::Migration, so you can't call it like that in the console.
If you want to add a default value for this column, create a new migration:
rails g migration add_default_value_to_show_attribute
Then in the migration created:
# That's the more generic way t...
How to reload a clojure file in REPL
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:reload-all should also work. The OP specifically says it doesn't, but I think there was something else wrong in the OP's dev environment because for a single file the two (:reload and :reload-all) should have the same effect. Here'...
error LNK2019: 无法解析的外部符号_socket，该符号在函数 中被引用 - C/C+...
error LNK2019: 无法解析的外部符号_socket，该符号在函数 中被引用1>NetClient.obj : error LNK2019: 无法解析的外部符号 _closesocket@4，该符号在函数 _main 中被引用1>NetClient.obj : error L...1>NetClient.obj : error LNK2019: 无法解析的外部符号 _closesocket@...
Build Eclipse Java Project from Command Line
...ore.aptBuild
It uses the jdt apt plugin to build your workspace automatically. This is also known as a 'Headless Build'. Damn hard to figure out. If you're not using a win32 exe, you can try this:
java -cp startup.jar -noSplash -data "D:\Source\MyProject\workspace" -application org.eclipse.jdt....
Longest line in a file
...ing for a simple way to find the length of the longest line in a file. Ideally, it would be a simple bash shell command instead of a script.
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How to deep copy a list?
... don't make a deep copy using list() (Both list(...) and testList[:] are shallow copies).
You use copy.deepcopy(...) for deep copying a list.
deepcopy(x, memo=None, _nil=[])
Deep copy operation on arbitrary Python objects.
See the following snippet -
>>> a = [[1, 2, 3], [4, 5, 6]]...
How is the undo tree used in Vim?
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See also :h undo-redo, which lists all the commands and their usage.
There are two ways to traverse the undo tree. One is to go "back in time". g+ and g- will traverse all of the nodes in the tree in chronological or reverse-chronological order (which can...
Simulate CREATE DATABASE IF NOT EXISTS for PostgreSQL?
...an work around it from within psql by executing the DDL statement conditionally:
SELECT 'CREATE DATABASE mydb'
WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'mydb')\gexec
The manual:
\gexec
Sends the current query buffer to the server, then treats each column of each row of the query's...
Does IMDB provide an API? [closed]
...lo.json (alternate)
Format: JSON-P
Caveat: It's in JSON-P format, and the callback parameter can not customised. To use it cross-domain you'll have to use the function name they choose (which is in the imdb${searchphrase} format). Alternatively, one could strip or replace the padding via a local pro...
How do I write the 'cd' command in a makefile?
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It is actually executing the command, changing the directory to some_directory, however, this is performed in a sub-process shell, and affects neither make nor the shell you're working from.
If you're looking to perform more tasks wit...