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UnmodifiableMap (Java Collections) vs ImmutableMap (Google) [duplicate]
... still possible:
realMap.put("E", "F");
// The change in the "realMap" is now also visible
// in the "unmodifiableMap". So the unmodifiableMap
// has changed after it has been created.
unmodifiableMap.get("E"); // Will return "F".
In contrast to that, the ImmutableMap of Guava is really immutabl...
How do I get the current date in JavaScript?
...It doesn't consider TimezoneOffset. At my time of testing, I was seeking "now" and I got "yesterday". stackoverflow.com/questions/13646446/…
– mickmackusa
Jun 26 '14 at 15:13
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PHP check whether property exists in object or class
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property_exists( mixed $class , string $property )
if (property_exists($ob, 'a'))
isset( mixed $var [, mixed $... ] )
if (isset($ob->a))
isset() will return false if property is null
Example 1:
$ob->a = null
var_dump(isset($ob->a)); // false
Example 2: ...
Generate JSON string from NSDictionary in iOS
... error:&error];
if (! jsonData) {
NSLog(@"%s: error: %@", __func__, error.localizedDescription);
return @"{}";
} else {
return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}
}
@e...
How to call C from Swift?
Is there a way to call C routines from Swift?
6 Answers
6
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Best way to select random rows PostgreSQL
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Given your specifications (plus additional info in the comments),
You have a numeric ID column (integer numbers) with only few (or moderately few) gaps.
Obviously no or few write operations.
Your ID column has to be indexed! A primary key...
Node.js, can't open files. Error: ENOENT, stat './path/to/file'
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Paths specified with a . are relative to the current working directory, not relative to the script file. So the file might be found if you run node app.js but not if you run node folder/app.js. The only exception to this is require('....
ModelSerializer using model property
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One note: The fields list in Meta is optional. If you omit fields, in the above example, you would get all the MyModel fields plus ext_link in the serialized data. And this is really awesome for complex models! EDIT: At least, this is true for djangorestframework==2.3.14....
常用Sql - 爬虫/数据库 - 清泛IT社区，为创新赋能！
本帖最后由 zqp2013 于 2015-3-17 22:06 编辑
mysql：drop table if exists tablename;
不能写成
drop table tablename if exists tablename;
mysql：建立索引Sql
CREATE TABLE tablename (
`ID` &nbs...
Rank function in MySQL
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+1 for the devious inline initialization, that's a beautiful trick.
– Charles
Jul 26 '10 at 9:42
29
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