OC Series Advanced-nsvalue

I. Nsvalue and NSNumber relations

Nsvalue is the parent of NSNumber, both of which convert data types to objects for ease of operation. The difference is: NSNumber is the basic data type of the sub-assembly, but the structure and pointers can not be transformed, this point nsvalue to a wide range, the structure and the pointer to the object, Nsvalue to do.

Two. Structure and object

1. First build a structure:

struct sct{    int 中文版;    float Math;} Score = {80,92.5f};

2. Structure to Object

        Intention? Wrap the structure type data into the Nsvalue
        First constant: The address of the struct is passed in so that we know where we want to store the data        //second constant: Convert the data type to be stored into a C-language string        nsvalue *value = [[Nsvalue alloc] Initwithbytes:&score objctype: @encode (struct SCT)];        NSLog (@ "%s", @encode (struct SCT));  This is a string that converts the data type of a struct into a C language

Output Result:

2016-06-29 20:17:55.527 nsvalue[555:85711] {sct=if}  //struct data type to C language string, I is int type, F is float type program ended with exit code:0

2. Actions to be done by objects: such as storing objects in a dictionary

        Nsdictionary *dic = [nsdictionary dictionarywithobjectsandkeys:value,@ "key", nil];        Nsvalue *value1 = [dic objectforkey:@ "key"];        NSLog (@ "%@", value1);

Value1 agreed to the result:

2016-06-29 20:26:05.652 nsvalue[579:112040] <50000000 0000b942>  //Object address program ended with exit code:0

3.NSValue reduced to a structural body

3.1 declaring an empty struct-body variable

struct SCT score2;

3.2 The structure of the value1 package into an empty structure variable in The 3.1 step

        &: Indicates where the data taken out of value1 is stored        [value1 getvalue:&score2];
        NSLog(@ "中文版 =%d,math =%f", Score2.  中文版, Score2.  Math);      

Output Result:

2016-06-29 20:38:57.380 nsvalue[603:155723] 中文版 = 80,math = 92.500000Program ended with exit code:0

Three. Pointers and objects

1. First create a pointer

Char *p = (char *) 0x1f;  Casting hexadecimal numbers

2. Pointer to Object

        Nsvalue *value3 = [[Nsvalue alloc]initwithbytes:&p Objctype: @encode (char *)];        NSLog (@ "%@", value3);

Output Result:

2016-06-29 20:51:16.940 nsvalue[624:197140] <1f000000 00000000>

3.NSValue revert to pointer

　　

　　

OC Series Advanced-nsvalue