可能重复:
我想知道class << self语句在模型类中意味着什么?它里面的陈述和外面的有什么不同呢?例如:
class Post < ActiveRecord::Base
class << self
def search(q)
# search from DB
end
end
def search2(qq)
# search from DB
end
end
class << self是什么意思?
方法search(q)和search2(qq)有什么区别?
我访问了<=>操作符所在的sql查询。<=>算子是什么意思?
SELECT STR_ID, TEX_TEXT AS STR_DES_TEXT, IF( EXISTS( SELECT * FROM SEARCH_TREE AS SEARCH_TREE2 WHERE SEARCH_TREE2.STR_ID_PARENT <=> SEARCH_TREE.STR_ID LIMIT 1 ), 1, 0) AS DESCENDANTS FROM SEARCH_TREE
这个sql是MySQL类型的。
mixed array_search ( mixed $needle , array $haystack [, bool $strict ] )
If the third parameter strict is set to TRUE then the array_search() function will also check the types of the needle in the haystack .
我不明白这是什么意思,也许举个例子能有所帮助?
我正在阅读关于Workers 的文章。
有一个代码示例,其中有一个单词"search“。什么意思?这是一个新命令吗?
var n = 1;
search: while (true) {
n += 1;
for (var i = 2; i <= Math.sqrt(n); i += 1)
if (n % i == 0)
continue search;
// found a prime!
postMessage(n);
}
我试着理解这段代码:
search_bst :: Tree -> String -> Maybe Int
search_bst Leaf _ = Nothing
search_bst (Node k v l r) sk =
if sk == k then Just v
else if sk < k then search_bst l sk
else search_bst r sk
我可以理解这个概念,但是Node k v l r是什么意思呢?这是否意味着search_bst接受两个参数,第一个参数是Node类型的实例,并且有三个值?
如何理解/etc/resolv.conf的格式?
$ cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "s
class Problem:
"""
This class outlines the structure of a search problem, but doesn't implement
any of the methods (in object-oriented terminology: an abstract class).
"""
def getStartState(self):
"""Returns the start state for
我使用apt 1.0.1ubuntu2 for amd64运行Ubuntu14.04。
我注意到跑步:
sudo apt search lib | grep nss
返回此警告消息:
WARNING: apt does not have a stable CLI interface yet. Use with caution in scripts.
并输出搜索结果后,由grep过滤(这是用apt-cache search lib | grep nss获得的相同结果)。
这个警告到底是什么意思?
我刚开始用百胜。这里有几个关于百胜的几个问题,我有三个命令
A > yum install package_name //search for package_name in local repo or the internet and install it
B > yum search package_name //search for package_name in local repo or the internet
C > yum list //list installed packages and packages that
我知道:
find . -perm -664
Search for files which have read and write permission for their owner and group,
and which other users can read.
但是我搞不懂04000和02000是什么意思,也许lsattr能告诉我?但我也对此一无所知。
谢谢。
有什么帮助吗?
我有这个代码(odoo 10)
email_from_ids = self.env['ir.config_parameter'].search(self, [('key', '=', 'auto_backup_from_email_Id')])
我有这个错误
TypeError: %d format: a number is required, not list
我不明白什么意思
我正在学习如何使用mongoDB,但我在使用tweepy时遇到了一些麻烦。
我只想用下面的代码做一个简单的twitter搜索:
lookup ='Notebooks' # Just a test case
api = API()
search = []
page = 1
tweets = api.search(lookup,page = page)
但是我得到了这个错误。
TweepError: Failed to send request: local variable 'auth' referenced before assignment
我不知道那是什么
在阅读有关AI (A*)和启发式的文章时,我遇到了这样的陈述:
Heuristics are sometimes defined for search nodes instead of states,
but this increased generality is rarely useful. (Why?)
谁能解释一下这是什么意思,举个例子,并回答为什么?有问题吗?