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1.nil >defines the ID of a null instance. Defines an instance that is empty, pointing to an empty pointer to an object in OC. > Sample code: NSString *somestring = nil; Nsurl *someurl = nil; ID someobject = nil; if (Anotherobject = = nil)//do

Recently I found myself writing JavaScript code is bloated, so I began to study the shorthand method of JavaScript. This will make our JavaScript code look refreshing and also improve our technology. So what's the shorthand for an empty judgment?

server| function Identity (Identity) column, and many people call it the self-add column, in SQL Server 2000, the identity column is defined by identity, and here is an example of a function related to getting the identity value of the last inserted

DriverManager class This class is used to load the driver, all of its members are static members, so there is no need to instantiate it in the program and access it directly through the class name. The DriverManager class is a JDBC management

The chain is the month and last month's difference in the proportion of the last month's value. In the complex OLAP computation we often use the concept of the Year-on-year chain, the requirements of the last dimension of a field of the

can you write a note? This problem has been bothering me since I wrote the code, and I believe it bothers other students as well. Previous write annotations have always been without a set of proven standards that have brought a lot of trouble to

InStr function Language Reference Version 1 Please see -------------------------------------------------------------------------------- Describe Returns the position of the first occurrence of a string in another string. Grammar INSTR ([Start,

This article mainly introduces the android to achieve horizontal sliding (transverse sliding) ListView example, this article with its own encapsulation of a control method to solve this requirement, the need for friends can refer to the The use of

The code is as follows $test = 0;if ($test = = ") {Echo ' in php, 0 is empty '; is output}if ($test = = = ") {Echo ' in php, 0 is empty '; Not to be output}if ($test ==null) {Echo ' in php, 0 is empty '; is output}if ($test

server|sqlserver| Tips To obtain all database information on a SQL Server using stored procedures sp_databases Execute command in query analysis exec sp_databases Result: Master 14464 NULL Model 1280 NULL msdb 14336 NULL Northwind 4352 NULL Pubs 25

Full use of--------------------join------------ Outer Joins. An outer join can be a left outer join, a right outer join, or a full outer join. When you specify an outer join in the FROM clause, you can specify one of the following groups of

　　A, JSP El language definition E L (Expression Language) Purpose: To make JSP easier to write. Expression languages are inspired by the ECMAScript and XPath expression languages, which provide a way to simplify expressions in a JSP. It is a