Deep dive into Swift frameworks

Fundamental definitions

To start with you must have a transparent understanding concerning the primary phrases. In case you already know what is the distinction between a module, package deal, library or framework you possibly can skip this part. Nonetheless when you nonetheless have some combined emotions about this stuff, please learn forward, you will not remorse it. 😉

Package deal

A package deal consists of Swift supply information and a manifest file.

A package deal is a group of Swift supply information. If you’re utilizing Swift Package deal Supervisor you even have to supply a manifest file with a view to make an actual package deal. If you wish to study extra about this software, you must examine my Swift Package deal Supervisor tutorial.

Instance: that is your package deal:

Sources
    my-source-file.swift
Package deal.swift

It’s also possible to take a look at the open sourced switf-corelibs-foundation package deal by Apple, which is used to construct the Basis framework for Swift.

Library

Library is a packaged assortment of object information that program can hyperlink towards.

So a library is a bunch of compiled code. You’ll be able to create two sorts of libraries:

From a very easy perspective the one distinction between them is the tactic of “integrating” aka. linking them into your mission. Earlier than I inform you extra about this course of, first we should always speak about object information.

Mach-O file format

To create packages, builders convert supply code to object information. The thing information are then packaged into executable code or static libraries.

While you’re compiling the supply information you might be principally making object information, utilizing the Mach-O (MachObject) file format. These information are the core constructing blocks of your functions, frameworks, and libraries (each dynamic and static).

Linking libraries

Linking refers back to the creation of a single executable file from a number of object information.

In different phrases:

After the compiler has created all the article information, one other program is known as to bundle them into an executable program file. That program is known as a linker and the method of bundling them into the executable is known as linking.

Linking is simply combining all of your object information into an executable and resolving all of the externals, so the system will be capable to name all of the features contained in the binary.

Static linking

The supply code of the library is actually going to be copied into the appliance’s supply. This can end in a giant executable, it will take extra time to load, so the binary could have a slower startup time. Oh, did I point out that if you’re attempting to hyperlink the identical library greater than as soon as, the method will fail due to duplicated symbols?

This technique has benefits as properly, for instance the executable will at all times include the right model of the library, and solely these components shall be copied into the principle software which might be actually used, so you do not have to load the entire stuff, nevertheless it looks as if dynamic linking goes to be higher in some circumstances.

Dynamic linking

Dynamic libraries usually are not embedded into the supply of the binary, they’re loaded at runtime. Which means apps could be smaller and startup time can considerably be sooner due to the light-weight binary information. As a free of charge dynamic libraries could be shared with a number of executables to allow them to have decrease reminiscence footprints. That is why typically they’re being referred as shared libraries.

After all if the dynamic library isn’t accessible – or it is accessible however ther model is incompatible – your software will not run or it will crash. However this may be a bonus, as a result of the writer of the dynamic library can ship fixes and your app can profit from these, with out recompilation.

Fortuitously system libraries like UIKit are at all times accessible, so you do not have to fret an excessive amount of about this difficulty…

Framework

A framework is a hierarchical listing that encapsulates shared assets, similar to a dynamic shared library, nib information, picture information, localized strings, header information, and reference documentation in a single package deal.

So let’s make this straightforward: frameworks are static or dynamic libraries packed right into a bundle with some further belongings, meta description for versioning and extra. UIKit is a framework which wants picture belongings to show a number of the UI parts, additionally it has a model description, by the best way the model of UIKit is similar because the model of iOS.

Module

Swift organizes code into modules. Every module specifies a namespace and enforces entry controls on which components of that code can be utilized outdoors of the module.

With the import key phrase you might be actually importing exterior modules into your sorce. In Swift you might be at all times utilizing frameworks as modules, however let’s return in time for some time to know why we wanted modules in any respect.

import UIKit
import my-awesome-module

Earlier than modules you needed to import framework headers immediately into your code and also you additionally needed to hyperlink manually the framework’s binary inside Xcode. The #import macro actually copy-pasted the entire resolved dependency construction into your code, and the compiler did the work on that vast supply file.

It was a fragile system, issues might go improper with macro definitions, you may simply break different frameworks. That was the explanation for outlining prefixed uppercased very lengthy macro names like: NS_MYSUPERLONGMACRONAME… 😒

There was an different difficulty: the copy-pasing resulted in non-scalable compile instances. So as to resolve this, precompiled header (PCH) information had been born, however that was solely a partial answer, as a result of they polluted the namespace (you understand when you import UIKit in a PCH file it will get accessible in in every single place), and noone actually maintained them.

Modules and module maps

The holy grail was already there, with the assistance of module maps (defining what sort of headers are a part of a module and what is the binary that has the implementation) we have encapsulated modular frameworks. 🎉 They’re individually compiled as soon as, the header information are defining the interface (API), and the (routinely) linked dylib file accommodates the implementation. Hurray, no must parse framework headers throughout compilation time (scalability), so native macro definitions will not break something. Modules can include submodules (inheritance), and you do not have to hyperlink them explicitly inside your (Xcode) mission, as a result of the .modulemap file has all the knowledge that the construct system wants.

Finish of the story, now you understand what occurs below the hood, once you import Basis or import UIKit.

Command line instruments

Now that you understand the logic behind the entire dynamic modular framework system, we should always begin analyzing the instruments that make this infrastructure potential.

All the time learn the person pages, aka. RTFM! In case you do not wish to learn that a lot, you possibly can obtain the instance mission from gitlab and open the makefiles for the essence. There shall be 3 fundamental classes: C, Swift and Xcode mission examples.

clang

the Clang C, C++, and Goal-C compiler

Clang is a compiler frontend for C languages (C, C++, Goal-C). In case you have ever tried to compiled C code with gcc throughout your college years, you possibly can think about that clang is kind of the identical as gcc, however these days it could possibly do much more.

clang -c fundamental.c -o fundamental.o #compiles a C supply file

LLVM: compiler backend system, which may compile and optimize the intermediate illustration (IR) code generated by clang or the Swift compiler for instance. It is language unbiased, and it could possibly achieve this many issues that might match right into a ebook, however for now to illustrate that LLVM is making the ultimate machine code in your executable.

swiftc

The Swift compiler, there isn’t any guide entry for this factor, however don’t fret, simply hearth up swiftc -h and see what can supply to you.

swiftc fundamental.swift #compiles a Swift supply file

As you possibly can see this software is what really can compile the Swift supply information into Mach-O’s or remaining executables. There’s a brief instance within the connected repository, you must examine on that if you would like to study extra concerning the Swift compiler.

ar

The ar utility creates and maintains teams of information mixed into an archive. As soon as an archive has been created, new information could be added and present information could be extracted, deleted, or changed.

So, in a nutshell you possibly can zip Mach-O information into one file.

ar -rcs myLibrary.a *.o

With the assistance of ar you had been capable of create static library information, however these days libtool have the identical performance and much more.

ranlib

ranlib generates an index to the contents of an archive and shops it within the archive. The index lists every image outlined by a member of an archive that may be a relocatable object file.

Ranlib can create an index file contained in the static lib, so issues are going to be sooner once you’re about to make use of your library.

ranlib myLibrary.a

So ranlib & ar are instruments for sustaining static libraries, normally ar takes care of the indexing, and you do not have to run ranlib anymore. Nonetheless there’s a higher possibility for managing static (and dynamic) libraries that you must study…

libtool

create libraries

With libtool you possibly can create dynamically linked libraries, or statically linked (archive) libraries. This software with the -static possibility is meant to switch ar & ranlib.

libtool -static *.o -o myLibrary.a

These days libtool is the principle possibility for increase library information, you must positively study this software when you’re into the subject. You’ll be able to examine the instance mission’s makefile for more information, or as normally you possibly can learn the manuals (man libtool). 😉

ld

The ld command combines a number of object information and libraries, resolves references, and produces an ouput file. ld can produce a remaining linked picture (executable, dylib, or bundle).

Let’s make it easy: that is the linker software.

ld fundamental.o -lSystem -LmyLibLocation -lmyLibrary -o MyApp

It could possibly hyperlink a number of information right into a single entity, so from the Mach-O’s you’ll make an executable binary. Linking is critical, as a result of the system must resolve the addresses of every technique from the linked libraries. In different phrases, the executable will be capable to run and your whole features shall be accessible for calling. 📱

nm

show title record (image desk)

With nm you possibly can see what symbols are inside a file.

nm myLibrary.a

As you possibly can see from the output, some sort of reminiscence addresses are related for a few of symbols. Those who have addresses are literally resolved, all of the others are coming from different libraries (they don’t seem to be resolved but). So which means they will be resolved at runtime. The opposite possibility is that you must hyperlink them. 😅

otool

object file displaying software

With otool you possibly can look at the contents of Mach-O information or libraries.

otool -L myLibrary.a
otool -tV myLibrary.a

For instance you possibly can record the linked libraries, or see the disassembled textual content contents of the file. It is a actually useful software when you’re accustomed to the Mach-O file format, additionally good one to make use of for reverse-engineer an present software.

lipo

create or function on common information

With the assistance of the lipo software you possibly can create common (multi-architecture) information. Normally this software is used for creating common frameworks.

lipo -create -output myFramework.framework units.framework simulator.framework

Think about the next situation: you construct your sources each for arm7 and i386. On an actual system you’d must ship the arm7 model, however for the iOS simulator you may want the i386 one. With the assistance of lipo you possibly can mix these architectures into one, and ship that framework, so the tip consumer haven’t got to fret about this difficulty anymore.

Learn on the article to see the way it’s accomplished. 👇

Xcode associated instruments

These instruments could be invoked from the command line as properly, however they are much extra associated to Xcode than those earlier than. Let’s have a fast walk-through.

xcode-select

Manages the lively developer listing for Xcode and BSD instruments. In case you have a number of variations of Xcode in your machine this software can simply swap between the developer instruments offered by the induvidual variations.

xcode-select --switch path/to/Xcode.app

xcrun

Run or find growth instruments and properties. With xcrun you possibly can principally run something you could handle from Xcode.

xcrun simctl record #record of simulators

codesign

Create and manipulate code signatures

It could possibly signal your software with the correct signature. Normally this factor failed once you had been attempting to signal your app earlier than automated signing was launched.

codesign -s "Your Firm, Inc." /path/to/MyApp.app
    codesign -v /path/to/MyApp.app

xcodebuild

construct Xcode initiatives and workspaces

That is it. It will parse the Xcode mission or workspace file and executes the suitable buid instructions primarily based on it.

xcodebuild -project Instance.xcodeproj -target Instance
    xcodebuild -list
    xcodebuild -showsdks

The way to make a closed supply common FATtened (multi-architecture) Swift framework for iOS?

So we’re right here, the entire article was made for studying the logic behind this tutorial.

To start with, I do not need to reinvent the wheel, as a result of there’s a fantastically written article that you must learn. Nonetheless, I would like to present you some extra detailed clarification and a bit modification for the scripts.

Skinny vs. fats frameworks

Skinny frameworks accommodates compiled code for just one structure. Fats frameworks alternatively are containing “slices” for a number of architectures. Architectures are principally referred as slices, so for instance the i386 or arm7 slice.

This implies, when you compile a framework just for i386 and x86_64 architectures, it’ll work solely on the simulator and horribly fail on actual units. So if you wish to construct a very common framework, you must compile for ALL the present architectures.

Constructing a fats framework

I’ve a excellent news for you. You simply want one little construct section script and an mixture goal with a view to construct a multi-architecture framework. Right here it’s, shamelessly ripped off from the supply article, with some further adjustments… 😁

set -e
BUILD_PATH="${SRCROOT}/construct"
DEPLOYMENT_PATH="${SRCROOT}"
TARGET_NAME="Console-iOS"
FRAMEWORK_NAME="Console"
FRAMEWORK="${FRAMEWORK_NAME}.framework"
FRAMEWORK_PATH="${DEPLOYMENT_PATH}/${FRAMEWORK}"


if [ -d "${BUILD_PATH}" ]; then
    rm -rf "${BUILD_PATH}"
fi


xcodebuild -target "${TARGET_NAME}" -configuration Launch 
    -arch arm64 -arch armv7 -arch armv7s 
    only_active_arch=no defines_module=sure -sdk "iphoneos"

xcodebuild -target "${TARGET_NAME}" -configuration Launch 
    -arch x86_64 -arch i386 
    only_active_arch=no defines_module=sure -sdk "iphonesimulator"


if [ -d "${FRAMEWORK_PATH}" ]; then
    rm -rf "${FRAMEWORK_PATH}"
fi


cp -r "${BUILD_PATH}/Launch-iphoneos/${FRAMEWORK}" "${FRAMEWORK_PATH}"


lipo -create -output "${FRAMEWORK_PATH}/${FRAMEWORK_NAME}" 
    "${BUILD_PATH}/Launch-iphoneos/${FRAMEWORK}/${FRAMEWORK_NAME}" 
    "${BUILD_PATH}/Launch-iphonesimulator/${FRAMEWORK}/${FRAMEWORK_NAME}"


cp -r "${BUILD_PATH}/Launch-iphonesimulator/${FRAMEWORK}/Modules/${FRAMEWORK_NAME}.swiftmodule/" 
    "${FRAMEWORK_PATH}/Modules/${FRAMEWORK_NAME}.swiftmodule"


if [ -d "${BUILD_PATH}" ]; then
    rm -rf "${BUILD_PATH}"
fi

You’ll be able to at all times look at the created framework with the lipo software.

lipo -info Console.framework/Console

Utilization

You simply need to embedd your model new framework into the mission that you just’d like to make use of and set some paths. That is it. Nearly…

Delivery to the App Retailer

There is just one difficulty with fats architectures. They include slices for the simulator as properly. If you wish to submit your app to the app retailer, you must minimize off the simulator associated codebase from the framework. The explanation behind that is that no precise actual system requires this chunk of code, so why submit it, proper?

APP_PATH="${TARGET_BUILD_DIR}/${WRAPPER_NAME}"


discover "$APP_PATH" -name '*.framework' -type d | whereas learn -r FRAMEWORK
do
    FRAMEWORK_EXECUTABLE_NAME=$(defaults learn "$FRAMEWORK/Information.plist" CFBundleExecutable)
    FRAMEWORK_EXECUTABLE_PATH="$FRAMEWORK/$FRAMEWORK_EXECUTABLE_NAME"
    echo "Executable is $FRAMEWORK_EXECUTABLE_PATH"

    EXTRACTED_ARCHS=()

    for ARCH in $ARCHS
    do
        echo "Extracting $ARCH from $FRAMEWORK_EXECUTABLE_NAME"
        lipo -extract "$ARCH" "$FRAMEWORK_EXECUTABLE_PATH" -o "$FRAMEWORK_EXECUTABLE_PATH-$ARCH"
        EXTRACTED_ARCHS+=("$FRAMEWORK_EXECUTABLE_PATH-$ARCH")
    accomplished

    echo "Merging extracted architectures: ${ARCHS}"
    lipo -o "$FRAMEWORK_EXECUTABLE_PATH-merged" -create "${EXTRACTED_ARCHS[@]}"
    rm "${EXTRACTED_ARCHS[@]}"

    echo "Changing unique executable with thinned model"
    rm "$FRAMEWORK_EXECUTABLE_PATH"
    mv "$FRAMEWORK_EXECUTABLE_PATH-merged" "$FRAMEWORK_EXECUTABLE_PATH"

accomplished

This little script will take away all of the pointless slices from the framework, so you’ll submit your app through iTunesConnect, with none points. (ha-ha-ha. 😅)

You need to add this final script to your software’s construct phases.

Closing ideas

If you wish to get faimiliar with the instruments behind the scenes, this text will provide help to with the fundamentals. I could not discover one thing like this however I needed to dig deeper into the subject, so I made one. I hope you loved it, be happy to submit a gitlab difficulty or contact me when you discover something improper or you have got an recommendation to enhance the article. 😉