External Interfaces Reference |
Get field value, given field number and index into structure array
C Syntax
#include "matrix.h" mxArray *mxGetFieldByNumber(const mxArray *array_ptr, int index, int field_number);
Arguments
array_ptr
Pointer to a structure mxArray
.
index
The desired element. The first element of an mxArray
has an index
of 0
, the second element has an index
of 1
, and the last element has an index
of N-1
, where N
is the total number of elements in the structure mxArray
. See mxCalcSingleSubscript
for more details on calculating an index.
field_number
The position of the field whose value you want to extract. The first field within each element has a field number of 0
, the second field has a field number of 1
, and so on. The last field has a field number of N-1
, where N
is the number of fields.
Returns
A pointer to the mxArray
in the specified field for the desired element, on success. Returns NULL
if passed an invalid argument or if there is no value assigned to the specified field. Common causes of failure include:
array_ptr
that does not point to a structure mxArray
. Call mxIsStruct
to determine if array_ptr
points to is a structure mxArray
.
mxGetFieldNumber
to determine the field number that corresponds to a given field name.
Description
Call mxGetFieldByNumber
to get the value held in the specified field_number
at the indexed element.
where index
is zero if you have a one-by-one structure.
Examples
See phonebook.c
in the refbook
subdirectory of the examples
directory.
For additional examples, see mxisclass.c
in the mx
subdirectory of the examples
directory and explore.c
in the mex
subdirectory of the examples
directory.
See Also
mxGetField
, mxGetFieldNameByNumber
, mxGetFieldNumber
, mxGetNumberOfFields
, mxSetField
, mxSetFieldByNumber
mxGetField | mxGetFieldNameByNumber |
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