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MQTT物联网协议完全实践指南 · App Inventor 2 中文网
...态处理
when UrsPahoMqttClient1.ConnectionStateChanged newState
do
if newState = 1 then // 连接成功
set CurrentRetry to 0
set Label_ConnectionStatus.Text to "已连接 - 在线"
set Label_ConnectionStatus.TextColor to Green
call subscribeToAllTopics
...
How do I set up a simple delegate to communicate between two view controllers?
.../ See http://stackoverflow.com/a/4796131/263871 for the rationale
// (Tip: If you're not using ARC, use `assign` instead of `weak`)
@property (nonatomic, weak) id<ChildViewControllerDelegate> delegate;
// A simple IBAction method that I'll associate with a close button in
// the UI. We'll cal...
How to find third or nth maximum salary from salary table?
...
Use ROW_NUMBER(if you want a single) or DENSE_RANK(for all related rows):
WITH CTE AS
(
SELECT EmpID, EmpName, EmpSalary,
RN = ROW_NUMBER() OVER (ORDER BY EmpSalary DESC)
FROM dbo.Salary
)
SELECT EmpID, EmpName, EmpSalar...
Find objects between two dates MongoDB
...
Querying for a Date Range (Specific Month or Day) in the MongoDB Cookbook has a very good explanation on the matter, but below is something I tried out myself and it seems to work.
items.save({
name: "example",
created_at: ISODate("2010-04-30T00:0...
Given two directory trees, how can I find out which files differ by content?
If I want find the differences between two directory trees, I usually just execute:
10 Answers
...
How can I read a large text file line by line using Java?
...null) {
// process the line.
}
}
You can read the data faster if you assume there is no character encoding. e.g. ASCII-7 but it won't make much difference. It is highly likely that what you do with the data will take much longer.
EDIT: A less common pattern to use which avoids the sco...
Is there an API to get bank transaction and bank balance? [closed]
...lso Bank of America)
and I want to get my bank transactions and my balance if I can.
Is there an API for that? in PHP or JAVA?
If so, please let me know how to get them.
...
MySQL query to get column names?
... best way is to use the INFORMATION_SCHEMA metadata virtual database. Specifically the INFORMATION_SCHEMA.COLUMNS table...
SELECT `COLUMN_NAME`
FROM `INFORMATION_SCHEMA`.`COLUMNS`
WHERE `TABLE_SCHEMA`='yourdatabasename'
AND `TABLE_NAME`='yourtablename';
It's VERY powerful, and can give yo...
Get the current git hash in a Python script
... This has the drawback that the version printing code will be broken if the code is ever run without the git repo present. For example, in production. :)
– JosefAssad
Feb 20 '13 at 21:18
...
How do you find the row count for all your tables in Postgres
...looking for a way to find the row count for all my tables in Postgres. I know I can do this one table at a time with:
15 A...