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• A Glimpse Of Xcode Ide
• A Glimpse Of Xcode Tutorial
• Glimpse Core
• A Glimpse Of Xcode Development

You can easily create programs, as modern operating systems are very easy to understand and begin programming. Apple has built a complete programming environment called Xcode. Xcode is an Integrated Development Environment (IDE). This means that Xcode is a complete studio for writing, compiling, debugging, and building software applications.

Contents

• 1 How to Use Xcode

How to Use Xcode

Launching Xcode. If nothing happens, download Xcode and try again. Launching Visual Studio. If nothing happens, download the GitHub extension for Visual Studio and try again. 13 commits Files Permalink. Failed to load latest commit information. Getting started with Codemagic CI/CD for React Native apps. After signing up, you can use React Native workflows by creating a new project in Codemagic and simply selecting the React Native App from the options. Xcode is still not perfect, but we all have to admit that each iteration makes a real difference. Let’s take a glimpse at what you can squeeze out from Xcode to make working with it a bit more pleasurable. Xcode has been part of iOS developers’ lives for a few years now. Xcode installs in a folder called Developer at the root of your startup drive. The Developer folder contains an Applications folder. This folders contains Xcode, and other applications, to help you develop web applications, audio, interfaces and so on. If you select the Documentation option, Xcode downloads all the files and keeps them updated.

Installing the Developer Tools

Compared to the full version of Microsoft’s Video Studio Professional, Xcode is simple and easy to use. It supports several programming languages, such as C, C++, Objective-C, Objective-C++, Java, AppleScript, OCaml, Fortran, ADA, and more. Most Apple developers use Objective-C, which is an object-oriented programming (OOP) language.

Xcode comes with Mac OS X, but it is not installed by default. You must install it from the installation disc. Alternatively, you can download the latest version of Xcode from Apple’s Developer Connection Website. Xcode installs in a folder called Developer at the root of your startup drive. The Developer folder contains an Applications folder. This folders contains Xcode, and other applications, to help you develop web applications, audio, interfaces and so on. If you select the Documentation option, Xcode downloads all the files and keeps them updated..

How to Join the Apple Developer Connection

Once you have Xcode installed, you should sign up for Apple Developer Connection. Once you join, you can download the latest version of Xcode. You can also download documentation, development videos, sample codes, and just about anything you need to get going as a coder.

There is also a series of developer programs, that you can join, and download beta versions of upcoming software, but you have to pay annual fees to join the Mac Developer Program and iOS Developer Program.

Note that beta versions can be unstable, so don’t install beta versions of software on your primary device. You should have separate test devices on hand for testing betas.

Important: If you sign up with the Mac Developer Program or iOS Developer Program, be sure to read the Agreement, especially the Nondisclosure Agreement (NDA), as Apple has very little patience with developers who talk and write about the Apple beta software. Under no circumstances should you post screenshots of Apple beta on the internet..

Learning the Xcode Interface

To start a new project with this code, select File – New Project. You can also click Create a New Xcode Project in the Welcome to Xcode window. The New Project window will open. It contains a series of templates for the different kinds of programs you can create. The sidebar divides templates into development environments. You’ll see options below each environment for specific kinds of programs, such as Applications Plug-In, Framework & Library, and System Plug-In.

Note that Mac OS X is included on the Mac OS X installation disc. However, the iOS template is required to download the iOS software development kit (SDK) from Apple Developer Connection.

Developer Documentation

You can access Developer Documentation at any point by using the Help menu. This menu provides several shortcuts to documentation files from Apple, including quick start guides and more. These files appear in the Developer Documentation window. However, most of the documents are oriented to be used by high-end users, but you can find documents aimed at people who’d like to learn how to program from scratch..

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This is an pretty good session about iOS memory. iOS Memory Deep Dive - WWDC 2018 - Videos - Apple Developer. I saw it and took some notes here.

Not all memory is created equal.

There are dirty memory, clean memory, compressed memory in iOS system. We have to know the differences between them.

Page

Page is typically 16KB in size and operating system gives it to you when your app requests memory.

Some pages can hold multiple objects, and some objects
can span multiple pages.

Pages Types

• Clean

  • Data that can be paged out of memory
  • Memory mapped files
  • frameworks*

• Dirty

  • memory written by an app
  • all heap allocations
  • decoded image buffers
• Comporessed

There is no traditional disk swap in iOS

Memory compressor

The system will do the compression and decompression for you by memory compressor.

What does Memory compressor do?

• Compresses unaccessed pages
• Decompresses pages upon access

Before being compressed:

After being compressed:

When you got Memory warning, you App is not always the cause. Maybe because the compressor freeing memory. Like, you receiving a phone call while using the App.

After being decompressed:

After removing objects in didReceiveMemoryWarning

Caching

• Trade-offs between CPU and memory. Caching can reduce the CPU usage and time complexity, but it costs memory.
• Remember the compressor. When decompressing, the used memory will be increased.
• Prefer NSCache over dictionary.

Memory Profile

It is the dirty size + the compressed size that the system uses to determine how much memory the app is really using.

We should mainly focuse on these two part, dirty and compressed memory when analyzing the memory profile.

Tools for Profiling Footprint

1. Xcode memory gauge
   

2. Instruments

• Allocations
• Leaks
• VM Tracker
  • providing profiles for dirty and compressed memories.
• Virtual memory trace

3. Debugger
   
4. memory graph

working with memory graph using commands

vmmap

vmmap helps to show some dirty memory info of your app. In general, we should look for the big number for the size.
There are virtual size, resident size, dirty size, swapped size columns here.

According to this session, we can ignore the virtual size, because it is memory requested by the app, while not neccessarily be used. swapped size is related to compressed memory. So we should care more about dirty size and swapped size.

An example of using vmmap to debug a memory issue

First, we can use summary info to look for the big numbers in virtual size and swapped size colomn. Here, we find CG Image takes much more memory than others.

Then, we use grep to get more info about CG Image.

There are two regions here, the last row is summary info. The secong CG Image region takes more takes more dirty and swapped memory. So we have to see more infomation of this region by using --verbose option.

All these commands can work with other shell commands, like redirecting the output stream a output.txt file.

And we will more regions.

It turns out that vmmap, by default, if it finds contiguous regions, it collapses. A general rule. the later region was created, the later my app’s life cycle it happened. Chance are this later region is more closely tied to whatever caused that memory pike.

So, we start to look at the last region. We can use the start memory address of the last region and search it in the memory graph in XCode.

Or use leak to get the trace tree. By scanning these info, we would find more clues.

Here, using malloc_history to see the back trace for this object, we found the related code creating this particular VM memory.

1. vmmap and AWK

A Glimpse Of Xcode Ide

This command can work with other commands.

leak

It not only shows the cycle, but also the root object of the cycle.

• leak circle
  

• root object
  

heap

• Shows objects allocated on the heap;
• useful for indentifying large objects in memory adn what allocated it.

heap command shows the class name in CLASS_NAME column, the num of the class in COUNT column, the average size of the object in the AVG column, the total size in the BYTES column.

malloc_history

In some cases, we not only want to know the memory size, but also want to know the how it created. So, here comes the malloc_history command.

A Glimpse Of Xcode Tutorial

• enable the malloc_stack logging

Which tool to pick

Glimpse Core

Use vmmap and heap to find some objects or regions with big number, use leak to see references between objects, like finding circular reference; use malloc_history to see how it is created.

A Glimpse Of Xcode Development

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