Runtime immutable groups __nsarray0 and __nsarrayi in IOS

Runtime immutable groups __nsarray0 and __nsarrayi in IOS

You may have all encountered an immutable group in a project to avoid the processing of arrays out of bounds: runtime, however, sometimes it does not solve all the problems, because the cluster is not the same

#import "Nsarray+security.h"

#import "Nsobject+swizzling.h"

@implementation Nsarray (Security)

+ (void) Load {

Static dispatch_once_t Oncetoken;

Dispatch_once (&oncetoken, ^{

[Objc_getclass ("__nsarray0") Methodswizzlingwithoriginalselector: @selector (objectatindex:) byswizzledselector:@ Selector (safeobjectatindex:)];

});

}

-(ID) Safeobjectatindex: (Nsuinteger) Index {

if (Self.count = = 0) {

NSLog (@ "%s can ' t get any object from an empty array", __function__);

return nil;

}

if (Index > Self.count) {

NSLog (@ "%s index out of bounds in array", __function__);

return nil;

}

return [self safeobjectatindex:index];

}

@end

But different ways of creating arrays result in different classes of clusters (which are actually different pointers), so let's look at

Nsarray *arr1 = @[@ "1", @ "2"];

Nsarray *ARR2 = [[Nsarray alloc]init];

Nsarray *ARR2 = [[Nsarray alloc]initwithobjocts:@ "1", nil];

Nsarray *ARR3 = [Nsarray alloc];

Nsmutblearray *ARR4 = [Nsmutblearray array];

You will find:

1, ARR2 class called _nsarray0
2, not init ARR3, the class name is called _nsplaceholderarray;
3, the variable array class name after initialization is called _nsarraym;
4, after the initialization of the immutable group class name is called _nsarrayi.

So be careful when doing runtime processing!

Runtime immutable groups __nsarray0 and __nsarrayi in IOS