mxGetField (External Interfaces/API Reference)

Get a field value, given a field name and an index in a structure array

Fortran Syntax

integer*4 function mxGetField(pm, index, fieldname)
integer*4 pm, index
character*(*) fieldname

Arguments

pm
Pointer to a structure mxArray.

index
The desired element. The first element of an mxArray has an index of 1, the second element has an index of 2, and the last element has an index of N, where N is the total number of elements in the structure mxArray.

fieldname
The name of the field whose value you want to extract.

Returns

A pointer to the mxArray in the specified field at the specified fieldname, on success. Returns zero if passed an invalid argument or if there is no value assigned to the specified field. Common causes of failure include:

Specifying a pm that does not point to a structure mxArray. To determine if pm points to a structure mxArray, call mxIsStruct.

Specifying an out-of-range index to an element past the end of the mxArray. For example, given a structure mxArray that contains 10 elements, you cannot specify an index greater than 10.

Specifying a nonexistent fieldname. Call mxGetFieldNameByNumber to get existing field names.

Insufficient heap space to hold the returned mxArray.

Description

Call mxGetField to get the value held in the specified element of the specified field.

mxGetFieldByNumber is similar to mxGetField. Both functions return the same value. The only difference is in the way you specify the field. mxGetFieldByNumber takes fieldnumber as its third argument, and mxGetField takes fieldname as its third argument.

Note Inputs to a MEX-file are constant read-only mxArrays and should not be modified. Using mxSetCell* or mxSetField* to modify the cells or fields of an argument passed from MATLAB causes unpredictable results.

Calling

```
mxGetField(pm, index, 'fieldname')
```

is equivalent to calling

fieldnum = mxGetFieldNumber(pm, 'fieldname')
mxGetFieldByNumber(pm, index, fieldnum)

where index is 1 if you have a one-by-one structure.

mxGetEps mxGetFieldByNumber