开放源代码的Swift：移动开发的新星

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"swift-recipes" 本书《Swift Recipes》是一本针对Swift编程语言的实践指南，采用问题-解决方案的结构，旨在帮助开发者深入理解和应用Swift。随着Apple在2015年的全球开发者大会（WWDC）上宣布开源Swift，并将其扩展到其他平台，这为开发者们提供了跨平台分享代码的巨大机会。在书中，作者T.Michael Rogers详细地介绍了Swift的各种概念和技术，覆盖了从基础到高级的多个方面。以下是对各章节内容的简要概述： 1. **Swift编程**：这部分内容可能涵盖了Swift的基础语法，变量和常量，控制流（如条件语句和循环），以及函数和闭包等核心概念。 2. **复杂类型**：讨论枚举、结构体和类，这些是构建自定义数据类型的关键工具。可能还包括协议和扩展，用于实现多态性和代码重用。 3. **集合**：涵盖了数组和字典这两种主要的集合类型，包括操作和遍历这些集合的方法，以及如何处理集合中的元素。 4. **高级Swift编程**：可能包含元组、可选类型、类型推断、泛型和错误处理等更深入的主题，这些都是Swift编程中不可或缺的部分。 5. **iOS应用开发**：介绍如何使用Swift构建iOS应用程序，可能涉及UIKit框架，用户界面设计，以及事件处理。 6. **OSX应用开发**：针对桌面平台，讨论Cocoa框架和Mac应用的特定功能。 7. **文件和目录**：讲解如何在Swift中读写文件，管理目录，以及进行文件I/O操作。 8. **并发**：涵盖Swift中的线程、GCD（Grand Central Dispatch）以及异步编程，帮助开发者理解和处理多任务执行。 9. **网络服务**：介绍如何与Web服务交互，包括API调用、JSON解析和HTTP请求。 10. **Core Data**：Apple的持久化框架，讨论如何使用Swift来存储和检索数据，以及模型-视图-控制器（MVC）架构的应用。 11. **高级iOS 8特性**：可能涵盖了iOS平台的一些高级特性，如通知中心小部件，健康Kit，以及第三方键盘支持等。最后，书中有索引方便读者查找特定主题，使得这本书成为开发者学习和解决Swift编程问题的重要参考资源。通过这本书，开发者不仅能深入理解Swift语言，还能掌握在iOS和OSX平台上构建高效应用程序的技能。

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12 CHAPTER 1: Swift Programming

When you are dealing with strings in Swift, always use countElements to determine the

number of composed characters in a string. Using NSString.length on a composed string

will give you an incorrect count if the string contains composed characters.

1-8. Manipulating Swift Strings

Problem

Every application at one time or another requires you to perform a manipulation of strings.

Swift strings are structured differently than NSString objects. Strings are value types in Swift

and behave differently than NSString objects. The method calls are similar between String

and NSString, but there are some key differences in names and parameters.

Solution

Swift strings have many built-in features. When a feature is not yet native to Swift, it makes

NSString methods available through bridging. Bridging allows you to pass Swift String

objects to Foundation classes in place of NSString. In addition, methods available to NSString

are made available to Swift String instances, which call the bridged NSString class method.

How It Works

In Swift, mutable strings are created using the var keyword. This allows the string to be

updated. If you use the let keyword, the string is immutable and cannot be modified. There

is some lack of clarity in the use of the labels “immutable” and “mutable.” Swift strings are

value types. As a result, when they are passed or assigned, a copy is made. At this time,

no NSMutableString functions are available through the String class in Swift. Therefore,

most functions return a string rather than operating on the original. The important thing to

remember is that if you want to change the contents of a variable, define it with var. If you

are not going to change the value, use let. The compiler can optimize those let statements.

To replace a string within a string, you will need to use the NSString function

stringByReplacingOccurrencesOfString:withString:

"The sky is red.".stringByReplacingOccurrencesOfString("red", withString: "blue")

In this function call, the string “red” will be replaced with “blue”. Sometimes, you may need

to replace a string, but you will want to restrict it to only part of the string.

"One, 2, 3.".stringByReplacingOccurrencesOfString("one", withString: "1",

options: NSStringCompareOptions.CaseInsensitiveSearch,

range: Range<String.Index>(start: str.startIndex,

end: advance(str.startIndex, 27 )))

The range parameter type is a Swift class called Range, and it is a range composed of

String.Index objects, a start and an end. A String.Index object is different from a typical

index. Because Swift strings can contain characters that are composed of multiple Unicode

13CHAPTER 1: Swift Programming

characters in an Extended Grapheme Cluster, a String.Index must refer to the position of

the composed character rather than the physical index. This means that string indexes for

different Swift strings cannot be used interchangeably.

To retrieve the starting index of a string, use String.startIndex. In order to get the String.

Index indicating the character five positions in, you use the global function advance(start:

String.Index, n: Int). Advance moves the String.Index n spots to the right. Don’t forget

to check for index violations. If “n” will advance past the end of the string, your program

will crash.

The statement advance("abc".startIndex,2) will return a String.Index two characters into

the string. In this case, it’s the position of the letter “b” because there are no decomposed

characters.

If you would like to get a substring of a string, there are a number of options, such as

substringFromIndex, substringToIndex and substringWithRange. Each requires

String.Index parameters or a Range of String.Index objects.

You can append strings using the + operator:

var phrase = "So long" + " and thanks for all the fish."

You can also use the += operator to append and reassign the string to itself:

var phrase = "So long"

phrase += " and thanks for all the fish."

Strings can be inserted into other strings using stringByReplacingCharactersInRange, but

they use the same index for the Range parameter.

var r = Range<String.Index>(start: advance(str.startIndex,6),

end: advance(str.startIndex,6))

"I like pizza.".stringByReplacingCharactersInRange(r, withString: " hot")

To delete a range of characters from a string, use stringByReplacingCharactersInRange with

an empty string.

var str = "I like hot pizza."

var r = Range<String.Index>(start: advance(str.startIndex,6), end:

advance(str.startIndex,10))

println(str.stringByReplacingCharactersInRange(r, withString: ""))

The Code and Usage

To run the following recipe code, enter it into an empty playground. If you need help creating

a playground, see Recipe 1-3. The Swift class String is bridged with NSString in the

Foundation library. This means you can call those methods on any Swift string. Listing 1-4 is

an example of some of those methods.

15CHAPTER 1: Swift Programming

Ranges can be used to return a substring from a String value. For example:

var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

str[str.startIndex...advance(str.startIndex, 13)]

This can be dangerous, however, because if you exceed the maximum index of the string,

you will get a runtime error. You need to check the end index of the string to be sure you do

not exceed the bounds. Always check against the range of the string.

You should test the amount you want to index into a string against countElements - 1. This

will return the maximum index that can be used. See the substring extension in the following

code. Be careful you don’t create an off-by-one error.

To test if a string is empty, you can call the global function isEmpty, which returns a Boolean:

isEmpty("123")

If you need to retrieve a number of characters from the beginning or end of a string, you can

use the prefix and suffix functions, respectively. The prefix function will retrieve the first N

characters from the String parameter, and N is the second parameter.

prefix("ABCDEFGHIJKLMNOPQRSTUVWXYZ",9) // returns "ABCDEFGHI"

The suffix method works the same way, except it returns the N characters, starting with the

last character and working backwards through the string.

suffix("ABCDEFGHIJKLMNOPQRSTUVWXYZ",9) // returns "RSTUVWXYZ"

The Code and Usage

Enter the code in Listing 1-5 into a playground window to see the examples in action.

This listing shows a number of examples of how you may use global Swift array functions

on strings. It also contains a class extension to the String class. This method will use global

array functions to return a substring of the original string. Remember strings are value types

in Swift, so this method will return a copy of the string.

Listing 1-5. Using array functions with strings

var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

// Prints each character of the alphabet in a line by itself

for c in str

{

print(c)

}

// Get a substring using a range of String.Index

str[str.startIndex...advance(str.startIndex, 13)]

// Return the first 9 characters of a string

prefix(str,9)

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开放源代码的Swift：移动开发的新星

使用Java结合Curator以及mysql编写一个简单的基于主从复制的分布式数据库,使用Curator-recipes5.0.0

使用Java编写一个主节点程序，使用Curator框架实现分布式锁和选举机制。主节点程序需要监听数据库变化，并将变化同步到从节点。使用Curator-recipes5.0.0

现有一些运行在特定端口上的服务器，每个服务器都连接着一个Mysql数据库，如何使用JAVA结合Curator实时监听每个服务器的实际状态，curator版本为curator-recipes5.0.0，Java版本为18，给出完整实现代码。

使得Curator注册的MySQL连接节点中存储的是实际的连接对象或连接状态，curator版本为curator-recipes5.0.0，Java版本为18，MySQL版本为8.0.21.给出完整实现代码。

如何使得Curator注册的MySQL连接节点中存储的是实际的连接对象或连接状态，curator版本为curator-recipes5.0.0，Java版本为18，MySQL版本为8.0.21.给出完整实现代码。

使用JAVA实现Curator注册的MySQL连接节点中存储的是实际的连接对象或连接状态，给出完整的注册过程实现代码，curator版本为curator-recipes5.0.0，Java版本为18，MySQL版本为8.0.21.给出完整实现代码以及使用示例。

使用Java结合Curator以及mysql编写一个简单的分布式数据库curator版本为curator-recipes5.0.0，Java版本为18，每个主节点，从节点均有一个mysql实例。并且整个分布式数据库有一个客户端可以执行SQL语句

使用Java结合Curator以及mysql编写一个简单的基于主从复制的分布式数据库curator版本为curator-recipes5.0.0，Java版本为18，每个主节点，从节点均有一个mysql实例。并且整个分布式数据库有一个客户端可以执行SQL语句。

petalinux没有meta-user/recipes-core

petalinux找不到linux/petalinux/project-spec/meta-user/recipes-kernel目标

uring parsing /home/shihongzhong/fsl-auto-yocto-bsp/sources/meta-alb/recipes-extended/opendds/opendds_git.bb

ERROR: Nothing RPROVIDES 'Network' (but /opt/petalinux/2018.3/NewZYNQ4/project-spec/meta-plnx-generated/recipes-core/images/petalinux-user-image.bb RDEPENDS on or otherwise requires it)

latex-workshop.latex.recipes

那你能帮我找一些关于shell编程的学习资料吗

Selenium最受欢迎的github项目

Bitbake still alive (no events for 600s). Active tasks: virtual:native:/home/wu/3568/yocto/build/../meta-clang/recipes-devtools/clang/clang_git.bb:do_compile /home/wu/3568/yocto/build/../meta-rockchip/recipes-kernel/linux/linux-rockchip_5.10.bb:do_compile

yocto编译中报错 Parsing recipes...ERROR: /home/wu/3568/yocto/meta-niic/niic/recipes-support/orocos/orocos-kdl_git.bb: Variable do_install_append contains an operation using the old override syntax. Please convert this layer/metadata before attempting to use with a newer bitbake.如何解决？

recipes-phosphor/

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