Logos: Difference between revisions

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Logos is a component of the [[Theos]] development suite that allows method hooking code to be written easily and clearly, using a set of special preprocessor directives.
{{soft redirect|https://theos.dev/docs/logos}}


== Overview ==
This article is obsolete, and has been replaced by the [https://theos.dev/docs/logos theos.dev website].


The syntax provided by Logos greatly simplifies the development of MobileSubstrate extensions ("tweaks") which can hook other methods throughout the OS.
If you need historical installation instructions, you can find the last version of this article [https://iphonedev.wiki/index.php?title=Logos&oldid=5734 here].
In this context, "method hooking" refers to a technique used to replace or modify methods of classes found in other applications on the phone.
 
== Getting Logos ==
 
Logos is distributed with [[Theos]], and you can use Logos' syntax in any Theos-built project without any extra setup.  For more information about Theos, visit [[Theos|its page]].
 
== Using Logos ==
 
=== Examples ===
 
Write me!
 
=== List of Logos Directives ===
 
==== Initialization ====
 
===== %init =====
 
    %init
    %init([<class>=<expr>, …])
    %init(Group[, [+|-]<class>=<expr>, …])
 
Initialize a group (or the default group). Passing no group name will initialize "_ungrouped", and passing class=expr arguments will substitute the given expressions for those classes at initialization time. The + sigil (as in class methods in Objective-C) can be prepended to the classname to substitute an expression for the metaclass. If not specified, the sigil defaults to -, to substitute the class itself. If not specified, the metaclass is derived from the class.
 
==== Block-level ====
 
The directives in this category open a block of code which must be closed by an %end directive (shown below).
 
===== %config =====
 
    %config(X=Y)
 
Set a logos configuration flag - currently unused, but the only existing configurable flag is 'generator', and the only generator that exists is "MobileSubstrate"
 
===== %hook =====
 
    %hook Classname
 
Open a hook block for the class named ''Classname''.
 
===== %subclass =====
 
    %subclass Classname
 
Superclass <Protocol, Protocol> // Subclass block - the class is created at runtime and populated with methods. ivars are not yet supported.
 
===== %group =====
 
    %group Groupname
 
Begin a hook group (for conditional initialization or code organization) with the name ''Groupname''. All ungrouped hooks are in the implicit "_ungrouped" group.
 
===== %class =====
 
    %class Class
 
Forward-declare a class. Outmoded by %c, but still exists. Creates a $Class variable, and initializes it with the "_ungrouped" group.
 
===== %new =====
 
    %new(signature)
 
Add a new method to a hooked class or subclass.
 
===== %ctor =====
 
    %ctor { … }
 
Generate an anonymous constructor (of default priority).
 
===== %end =====
 
    %end
 
Close a hook/subclass/group block.
 
==== Inline ====
 
===== %c =====
 
    %c(Class)
 
Effectively evaluates to Class, at runtime. Technically, creates $Class and populates it when the "_ungrouped" group is initialized.
 
===== %orig =====
 
    %orig
    %orig(args)
 
Call the original hooked method. Doesn't function in a %new'd method. Works in subclasses, strangely enough, because MobileSubstrate will generate a supercall closure at hook time. (If the hooked
method doesn't exist in the class we're hooking, it creates a stub that just calls the superclass implementation.) args is passed to the original function - don't include self and _cmd, Logos does this for you.
 
===== %log =====
 
    %log
 
Dump the method arguments to syslog.
 
[[Category:Development Tools]]

Latest revision as of 18:12, 19 February 2022

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https://theos.dev/docs/logos

This article is obsolete, and has been replaced by the theos.dev website.

If you need historical installation instructions, you can find the last version of this article here.