Key value pair

Key value pair writing format

In key value pairs, the key must be a string, but the value can be of type bool/string/int/float:

When writing key value pairs, there is no space between key and: but there is a space between value and:.

Replace sub tags in launch within yaml file:

Use with the rosparam sub tag in the launch file. See:

roslaunch/XML - ROS Wikihttp://wiki.ros.org/roslaunch/XML#substitution_args

The most detailed implementation of launch file and meta function package in ROS (example + code + parameter analysis)_ Super powerful blog - CSDN bloghttps://blog.csdn.net/weixin_45590473/article/details/122647788 Note: when the double quotation mark / single quotation mark of value contains "single quotation mark" or "double quotation mark", the transfer character \:

Reference to key value pair

The reference format is as follows: VAR_ name: &refer_ name

When writing a reference, there must be a space between the reference symbol & and:, and no space between & and the variable reference alias.

Cast type

yaml currently supports the following data type conversions:

Source data type	Target data type	Cast type converter
string	Int	!!int
string	float	!!float
Int	string	!!str
float	string	!!str

Note: when converting string to int type, there can be no decimal point in the string!

array

Normal array

The elements in the array can be key value pairs of type / bool/string/int/float:

In the array, in order to represent the hierarchical relationship, you must use the TAB key! The following error example:

The reason for the error is that the tab key is not used to display the hierarchical relationship!

Key value pair array

Array reference

Note: "-" represents the dimension. Each element in the above one-dimensional array is placed under a "-".

The application of array reference is as follows:

The meaning of * Arrag is the same as that of the reference coincidence & dereference symbol * in C language_ Name means "all elements under array arrag_name".

Multidimensional array

The high-dimensional array structure is shown in the following figure:

In fact, we can also use reference to build a high-dimensional array:

Namespace

Assignment method of common variables under namespace

In fact, we will use a prefix in the namespace structure of variables of different types, which is more like C

Base_name	Namespace	name
Var1	Namespace01	Namespace01/var1
Var2	Namespace01	Namespace01/var2

Use references to assign values to variables under namespaces

After using * to dereference Arrag01, assign all the values in Arrag01 array to var2 variable under namespace01 namespace, which is equivalent to:

Use references to import variables into namespaces

The above is to import the contents of one variable into another variable. Now, we import the contents of one variable into the namespace, but remember that "the imported contents must be composed of variables":

How to understand "all imported contents must be composed of variables"? Let's take an example to see if the following example can run?

It seems feasible. Let's expand it to see:

​#Quote
Arrag02:  
  ""Xiao Ming"  
  ""Li Hua"  
  "Daqiang“  

Is that right? Obviously, there is no variable under the Arrag02 namespace (variables in yaml exist in the form of key value pairs)! Then we are implementing the following example:

Errors will also be reported, because when we expand, we will find:

There is also no complete variable under the Arrag02 namespace. Therefore, we draw the following conclusions:

When using < <: * refer_ When name imports variables into the namespace, refer_name cannot be a reference to a key value pair, nor can it be a reference to an ordinary array. Generally, refer_name is a reference to multidimensional array / namespace.