efficiently. If you store strings in a cell array, then you lose the advantages of using a string
array.
However, if your code accepts heterogeneous cell arrays as inputs, then consider accepting cell
arrays that contain strings. You can convert any strings in such a cell array to character
vectors.
• In general, do not change the output type.
• If your function returns a character vector or cell array of character vectors, then do not
change the output type, even if the function accepts string arrays as inputs. For example, the
fileread function accepts an input file name specified as either a character vector or a
string, but the function returns the file contents as a character vector. By keeping the output
type the same, you can maintain backward compatibility.
• Return the same data type when the function modifies input text.
• If your function modifies input text and returns the modified text as the output argument, then
the input and output arguments should have the same data type. For example, the lower
function accepts text as the input argument, converts it to all lowercase letters, and returns it.
If the input argument is a character vector, then lower returns a character vector. If the input
is a string array, then lower returns a string array.
• Consider adding a 'TextType' argument to import functions.
• If your function imports data from files, and at least some of that data can be text, then
consider adding an input argument that specifies whether to return text as a character array or
a string array. For example, the readtable function provides the 'TextType' name-value
pair argument. This argument specifies whether readtable returns a table with text in cell
arrays of character vectors or string arrays.
Classes
• Treat methods as functions.
• For string adoption, treat methods as though they are functions. Accept string arrays as input
arguments, and in general, do not change the data type of the output arguments, as described
in the previous section.
• Do not change the data types of properties.
• If a property is a character vector or a cell array of character vectors, then do not change its
type. When you access such a property, the value that is returned is still a character vector or a
cell array of character vectors.
As an alternative, you can add a new property that is a string, and make it dependent on the
old property to maintain compatibility.
• Set properties using string arrays.
• If you can set a property using a character vector or cell array of character vectors, then
update your class to set that property using a string array too. However, do not change the
data type of the property. Instead, convert the input string array to the data type of the
property, and then set the property.
• Add a string method.
Update Your Code to Accept Strings
6-65
array.
However, if your code accepts heterogeneous cell arrays as inputs, then consider accepting cell
arrays that contain strings. You can convert any strings in such a cell array to character
vectors.
• In general, do not change the output type.
• If your function returns a character vector or cell array of character vectors, then do not
change the output type, even if the function accepts string arrays as inputs. For example, the
fileread function accepts an input file name specified as either a character vector or a
string, but the function returns the file contents as a character vector. By keeping the output
type the same, you can maintain backward compatibility.
• Return the same data type when the function modifies input text.
• If your function modifies input text and returns the modified text as the output argument, then
the input and output arguments should have the same data type. For example, the lower
function accepts text as the input argument, converts it to all lowercase letters, and returns it.
If the input argument is a character vector, then lower returns a character vector. If the input
is a string array, then lower returns a string array.
• Consider adding a 'TextType' argument to import functions.
• If your function imports data from files, and at least some of that data can be text, then
consider adding an input argument that specifies whether to return text as a character array or
a string array. For example, the readtable function provides the 'TextType' name-value
pair argument. This argument specifies whether readtable returns a table with text in cell
arrays of character vectors or string arrays.
Classes
• Treat methods as functions.
• For string adoption, treat methods as though they are functions. Accept string arrays as input
arguments, and in general, do not change the data type of the output arguments, as described
in the previous section.
• Do not change the data types of properties.
• If a property is a character vector or a cell array of character vectors, then do not change its
type. When you access such a property, the value that is returned is still a character vector or a
cell array of character vectors.
As an alternative, you can add a new property that is a string, and make it dependent on the
old property to maintain compatibility.
• Set properties using string arrays.
• If you can set a property using a character vector or cell array of character vectors, then
update your class to set that property using a string array too. However, do not change the
data type of the property. Instead, convert the input string array to the data type of the
property, and then set the property.
• Add a string method.
Update Your Code to Accept Strings
6-65