get

Get ROS parameter value

Syntax

pvalue = get(ptree)

pvalue = get(ptree,paramname)

pvalue = get(ptree,namespace)

[pvalue,status] = get(ptree,paramname)

pvalue = get(ptree,paramname,"DataType",ptype)

Description

pvalue = get(ptree) returns a dictionary of parameter values under the root namespace: /. The dictionary is stored in a structure.

pvalue = get(ptree,paramname) gets the value of the parameter with the name paramname from the parameter tree object ptree.

pvalue = get(ptree,namespace) returns a dictionary of parameter values under the specified namespace.

The following ROS data types are supported as values of parameters. For each ROS data type, the corresponding MATLAB^® data type is also listed.

• 32-bit integer — int32

• Boolean — logical

• double — double

• strings — string scalar, string, or character vector, char

• list — cell array (cell)

• dictionary — structure (struct)

[pvalue,status] = get(ptree,paramname) returns the parameter values and the associated status. status indicates whether the pvalue successfully returned.

pvalue = get(ptree,paramname,"DataType",ptype) specifies the ROS parameter data type when generating code. The input parameter type value must match the existing parameter type else the function returns the pvalue as empty, [], for the requested type.

Examples

Set and Get Parameter Value

Create the parameter tree. A ROS network must be available using rosinit.

rosinit

Launching ROS Core...
Done in 0.36336 seconds.
Initializing ROS master on http://172.23.109.169:59786.
Initializing global node /matlab_global_node_99328 with NodeURI http://dcc3881203glnxa64:42483/ and MasterURI http://localhost:59786.

ptree = rosparam;

Set a parameter value. You can also use the simplified version without a parameter tree:

rosparam set 'DoubleParam' 1.0

set(ptree,'DoubleParam',1.0)

Get the parameter value.

get(ptree,'DoubleParam')

ans = 
1

Alternatively, use the simplified versions without using the parameter tree.

rosparam set 'DoubleParam' 2.0
rosparam get 'DoubleParam'

2

Disconnect from ROS network.

rosshutdown

Shutting down global node /matlab_global_node_99328 with NodeURI http://dcc3881203glnxa64:42483/ and MasterURI http://localhost:59786.
Shutting down ROS master on http://172.23.109.169:59786.

Input Arguments

ptree — Parameter tree

ParameterTree object handle

Parameter tree, specified as a ParameterTree object handle. Create this object using the rosparam function.

paramname — ROS parameter name

string scalar | character vector

ROS parameter name, specified as a character vector. This string must match the parameter name exactly.

namespace — ROS parameter namespace

string scalar | character vector

ROS parameter namespace, specified as a string scalar or character vector. All parameter names starting with this string are listed when calling rosparam("list",namespace).

ptype — ROS parameter data type

'int32' | 'logical' | 'double' | 'char'

ROS parameter data type, specified as either 'int32', 'logical', 'double', or 'char'.

Output Arguments

pvalue — ROS parameter value or dictionary of values

int32 | logical | double | character vector | cell array | structure

ROS parameter value, returned as a supported MATLAB data type. When specifying the namespace input argument, pvalue is returned as a dictionary of parameter values under the specified namespace. The dictionary is represented in MATLAB as a structure.

The following ROS data types are supported as values of parameters. For each ROS data type, the corresponding MATLAB data type is also listed.

• 32-bit integer — int32

• Boolean — logical

• double — double

• string — character vector (char)

• list — cell array (cell)

• dictionary — structure (struct)

status — Status of ROS parameter value

true | false

Status of ROS parameter value, returned as true or false. If the status is false, the pvalue value is returned as empty, [].

Data Types: logical

Limitations

Base64-encoded binary data and iso 8601 data from ROS are not supported.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

This function supports C/C++ code generation with the limitations:

For code generation, only the following ROS data types are supported as values of parameters,

• 32-bit integer — int32

• Boolean — logical

• double — double

• strings — string scalar, string, or character vector, char

Version History

Introduced in R2019b