refactor: Convert MPPersistenceController to Obj C

[BrandonStalnaker]

Background

• The MPPersistenceController was implemented as an Objective-C++ file (.mm) which required the C++ standard library ( and ) for SQL statement handling and collection management
• Objective-C++ files have slower compilation times and add complexity to the build process
• The C++ features used were limited to basic string operations and vectors that can be easily replaced with Foundation equivalents (NSString, NSMutableArray)
• This change is necessary for us to switch to source based distribution for SPM

What Has Changed

• Converted MPPersistenceController.mm to pure Objective-C (MPPersistenceController.m)
• • Replaced std::string with NSString * and const char * for SQL statements
• • Replaced std::vector with NSMutableArray * for collecting query results
• • Replaced C++ string concatenation with NSMutableString and appendFormat:
• • Replaced std::to_string() with [NSString stringWithFormat:]
• • Replaced range-based for loops with Objective-C for-in enumeration
• • Removed using namespace std; and C++ headers
• Renamed MPPersistenceControllerTests.mm to MPPersistenceControllerTests.m (no C++ features were used in the test file)
• Updated project.pbxproj to reference the new .m files with correct lastKnownFileType
• Added additional unit tests for:
• • Breadcrumb save and pruning operations
• • Session archiving and duplicate detection
• • Database open/close operations
• • App and device info retrieval
• • Delete all sessions except specified session
• • Session update operations
• • Max bytes per event/batch calculations

Checklist

• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• I have tested this locally.

Reference Issue (For employees only. Ignore if you are an outside contributor)

• Closes https://rokt.atlassian.net/browse/SDKE-721

[github-actions]

📦 SDK Size Impact Report

Measures how much the SDK adds to an app's size (with-SDK minus without-SDK).

Metric	Target Branch	This PR	Change
App Bundle Impact	1.66 MB	1.62 MB	-40 KB
Executable Impact	896 bytes	896 bytes	+N/A
XCFramework Size	7.94 MB	7.39 MB	-564 KB

➡️ SDK size impact change is minimal.

Raw measurements

Target branch (workstation/9.0-Release):

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1784,"with_sdk_executable_size_bytes":76360,"sdk_impact_kb":1700,"sdk_executable_impact_bytes":896,"xcframework_size_kb":8132}

This PR:

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1744,"with_sdk_executable_size_bytes":76360,"sdk_impact_kb":1660,"sdk_executable_impact_bytes":896,"xcframework_size_kb":7568}

[denischilik]

Do we need to return copy of object?

[jamesnrokt]

Isn't it correct to return a copy here for immutability? The return type of the function is NSArray not NSMutableArray

[denischilik]

Since the array is created locally and not stored anywhere, returning a copy doesn’t add meaningful immutability guarantees here and only introduces an extra allocation. Returning an NSMutableArray instance as NSArray is valid, as NSMutableArray is a subclass of NSArray. Mutability is defined by the contract exposed to the caller: the client only sees an NSArray interface.

[denischilik]

It’s not a big deal, but avoiding the extra copy would keep things simpler and slightly more efficient here.