Change in reference count before and after copy modification for NSString

1NSLog (@"NSString object, use NSString to pick up the---------------------------------");2NSString *string1 = [[NSString Alloc]initwithformat:@"Immutable String"];3NSLog (@"reference count of immutable strings before copy =%ld", [string1 retaincount]);4         5NSString *copystring1 =string1.copy;6NSLog (@"reference count of immutable strings after copy =%ld", [string1 retaincount]);7NSLog (@"after copy, the reference count of copystring =%ld", [copyString1 Retaincount]);8         9NSLog (@"%p", string1);TenNSLog (@"%p", copyString1); OneNSLog (@"nsmutablestring object, use nsmutablestring to pick up the---------------------------------"); Ansmutablestring *string2 = [[nsmutablestring Alloc]initwithformat:@"variable String"]; -NSLog (@"reference count of mutable strings before copy =%ld", [string2 Retaincount]); -          theNsmutablestring *copystring2 =string2.copy; -NSLog (@"reference count of mutable strings after copy =%ld", [string2 Retaincount]); -NSLog (@"after copy, the reference count of copystring =%ld", [copyString2 Retaincount]); -          +NSLog (@"%p", string2); -NSLog (@"%p", copyString2); +NSLog (@"NSString object, use nsmutablestring to pick up the---------------------------------"); ANSString *string3 = [[NSString Alloc]initwithformat:@"Immutable String"]; atNSLog (@"reference count of immutable strings before copy =%ld", [String3 Retaincount]); -          -Nsmutablestring *copystring3 =string3.copy; -NSLog (@"reference count of immutable strings after copy =%ld", [String3 Retaincount]); -NSLog (@"after copy, the reference count of copystring =%ld", [CopyString3 Retaincount]); -          inNSLog (@"%p", string3); -NSLog (@"%p", copyString3); toNSLog (@"nsmutablestring object, use NSString to pick up the---------------------------------"); +nsmutablestring *string4 = [[nsmutablestring Alloc]initwithformat:@"variable String"]; -NSLog (@"reference count of mutable strings before copy =%ld", [String4 Retaincount]); the          *NSString *copystring4 =string4.copy; $NSLog (@"reference count of mutable strings after copy =%ld", [String4 Retaincount]);Panax NotoginsengNSLog (@"after copy, the reference count of copystring =%ld", [CopyString4 Retaincount]); -          theNSLog (@"%p", String4); +NSLog (@"%p", CopyString4);

Let's take a look at the running results above and print out what: 1 -- all:06.411 oclession9[1810:63941] NSString object, use NSString to pick up the---------------------------------

2  .- .- the  One: the:06.411oclession9[1810:63941] before copy, the reference count of immutable strings =13  .- .- the  One: the:06.411oclession9[1810:63941] After copy, the reference count of the immutable string =24  .- .- the  One: the:06.411oclession9[1810:63941] After copy, the reference count for copystring =25  .- .- the  One: the:06.411oclession9[1810:63941]0x1002027406  .- .- the  One: the:06.411oclession9[1810:63941]0x1002027407  .- .- the  One: the:06.412oclession9[1810:63941] Nsmutablestring object, use nsmutablestring to pick up the---------------------------------8  .- .- the  One: the:06.412oclession9[1810:63941] before copy, the reference count of a mutable string =19  .- .- the  One: the:06.412oclession9[1810:63941] After copy, the reference count of the mutable string =1Ten  .- .- the  One: the:06.412oclession9[1810:63941] After copy, the reference count for copystring =1 One  .- .- the  One: the:06.412oclession9[1810:63941]0x100300840 A  .- .- the  One: the:06.412oclession9[1810:63941]0x100300810 -  .- .- the  One: the:06.412oclession9[1810:63941] NSString object, use nsmutablestring to pick up the--------------------------------- -  .- .- the  One: the:06.412oclession9[1810:63941] before copy, the reference count of immutable strings =1 the  .- .- the  One: the:06.412oclession9[1810:63941] After copy, the reference count of the immutable string =2 -  .- .- the  One: the:06.412oclession9[1810:63941] After copy, the reference count for copystring =2 -  .- .- the  One: the:06.412oclession9[1810:63941]0x100106f90 -  .- .- the  One: the:06.412oclession9[1810:63941]0x100106f90 +  .- .- the  One: the:06.413oclession9[1810:63941] Nsmutablestring object, use NSString to pick up the--------------------------------- -  .- .- the  One: the:06.413oclession9[1810:63941] before copy, the reference count of a mutable string =1 +  .- .- the  One: the:06.413oclession9[1810:63941] After copy, the reference count of the mutable string =1 A  .- .- the  One: the:06.413oclession9[1810:63941] After copy, the reference count for copystring =1 at  .- .- the  One: the:06.413oclession9[1810:63941]0x1006002f0
2016-06-15 11:39:06.413 oclession9[1810:63941] 0x100600210

Conclusion: For a string, only the immutable copy of the immutable string is a shallow copy, and the rest is a deep copy.

Change in reference count before and after copy modification for NSString