throw - Throw exception - MATLAB (original) (raw)

Syntax

Description

throw([exception](#bud2s44-exception)) throws an exception based on the information contained in the MException object, exception. The exception terminates the currently running function and returns control either to the keyboard or to an enclosing catch block. When you throw an exception from outside a try/catch statement, MATLAB® displays the error message in the Command Window.

The throw function, unlike the throwAsCaller and rethrow functions, creates the stack trace from the location where MATLAB calls the function.

You can access the MException object via a try/catch statement or the MException.last function.

example

Examples

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Throw an exception if an input variable name does not exist in the workspace.

str = input('Type a variable name: ','s'); if ~exist(str,'var') ME = MException('MyComponent:noSuchVariable', ... 'Variable %s not found',str); throw(ME) end

At the input prompt, enter any variable that does not exist in your workspace. For example, enter notaVariable.

Variable notaVariable not found

Since notVariable doesn’t exist in your workspace, MATLAB creates and throws an MException object.

Create a function, combineArrays, in your working folder.

function C = combineArrays(A,B) try C = catAlongDim1(A,B); % Line 3 catch exception throw(exception) % Line 5 end end

function V = catAlongDim1(V1,V2) V = cat(1,V1,V2); % Line 10 end

Call the combineArrays function with arrays of different sizes.

A = 1:5; B = 1:4;

combineArrays(A,B)

Error using combineArrays Dimensions of matrices being concatenated are not consistent.

The stack refers to line 5 where MATLAB throws the exception.

Replace throw(exception) with rethrow(exception) on line 5 of the combineArrays function, and call the function again.

Error using cat Dimensions of matrices being concatenated are not consistent.

Error in combineArrays>catAlongDim1 V = cat(1,V1,V2);

Error in combineArrays C = catAlongDim1(A,B);

The rethrow function maintains the original stack and indicates the error is on line 3.

Input Arguments

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Exception containing the cause and location of an error, specified as a scalarMException object.

Extended Capabilities

Version History

Introduced in R2007b