How can I count the number of properties in a struct or JSON document?

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1
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I'm making a PDF generator in Go and one of the sections of it will be a table. To create a table I need to state the width of the columns, and this will be done by getting the page width (minus margins) and dividing by the number of columns in the table

The columns in the table are defined in a struct like this:

type Person struct {

    Name    string `json:"Name"`

    Age     string `json:"Age"`

    Comment string `json:"Comment"`

}

And JSON is unmarshalled into it

I don't want to have to hardcode '3' as the column number into my code and want to know how I can programmatically count the properties either in from the JSON or the struct itself

I've spent a few days searching now, and all results focus on people having trouble getting the values, but I want the keys!

Thanks in advance

asked Nov 19 at 10:59

MassiveOwl

468313

there is no way other than using reflect package, but I strongly suggest change your approach
– danicheeta
Nov 19 at 11:01

Can I ask why? The PDF package is Gofpdf, to generate a table it basically 'draws' individual cells and then stitches them together, meaning you have to get the individual cell width
– MassiveOwl
Nov 19 at 11:06

1

@danicheeta: Why? Reflection is necessary for this problem anyway.
– Flimzy
Nov 19 at 11:17

add a comment |

up vote
1
down vote

favorite

The columns in the table are defined in a struct like this:

type Person struct {

    Name    string `json:"Name"`

    Age     string `json:"Age"`

    Comment string `json:"Comment"`

}

And JSON is unmarshalled into it

I don't want to have to hardcode '3' as the column number into my code and want to know how I can programmatically count the properties either in from the JSON or the struct itself

I've spent a few days searching now, and all results focus on people having trouble getting the values, but I want the keys!

Thanks in advance

asked Nov 19 at 10:59

MassiveOwl

468313

there is no way other than using reflect package, but I strongly suggest change your approach
– danicheeta
Nov 19 at 11:01

Can I ask why? The PDF package is Gofpdf, to generate a table it basically 'draws' individual cells and then stitches them together, meaning you have to get the individual cell width
– MassiveOwl
Nov 19 at 11:06

1

@danicheeta: Why? Reflection is necessary for this problem anyway.
– Flimzy
Nov 19 at 11:17

add a comment |

up vote
1
down vote

favorite

The columns in the table are defined in a struct like this:

type Person struct {

    Name    string `json:"Name"`

    Age     string `json:"Age"`

    Comment string `json:"Comment"`

}

And JSON is unmarshalled into it

I don't want to have to hardcode '3' as the column number into my code and want to know how I can programmatically count the properties either in from the JSON or the struct itself

I've spent a few days searching now, and all results focus on people having trouble getting the values, but I want the keys!

Thanks in advance

asked Nov 19 at 10:59

MassiveOwl

468313

The columns in the table are defined in a struct like this:

type Person struct {

    Name    string `json:"Name"`

    Age     string `json:"Age"`

    Comment string `json:"Comment"`

}

And JSON is unmarshalled into it

I don't want to have to hardcode '3' as the column number into my code and want to know how I can programmatically count the properties either in from the JSON or the struct itself

I've spent a few days searching now, and all results focus on people having trouble getting the values, but I want the keys!

Thanks in advance

json go

asked Nov 19 at 10:59

MassiveOwl

468313

asked Nov 19 at 10:59

MassiveOwl

468313

asked Nov 19 at 10:59

MassiveOwl

468313

asked Nov 19 at 10:59

MassiveOwl

468313

asked Nov 19 at 10:59

MassiveOwl

468313

there is no way other than using reflect package, but I strongly suggest change your approach
– danicheeta
Nov 19 at 11:01

Can I ask why? The PDF package is Gofpdf, to generate a table it basically 'draws' individual cells and then stitches them together, meaning you have to get the individual cell width
– MassiveOwl
Nov 19 at 11:06

1

@danicheeta: Why? Reflection is necessary for this problem anyway.
– Flimzy
Nov 19 at 11:17

add a comment |

there is no way other than using reflect package, but I strongly suggest change your approach
– danicheeta
Nov 19 at 11:01

Can I ask why? The PDF package is Gofpdf, to generate a table it basically 'draws' individual cells and then stitches them together, meaning you have to get the individual cell width
– MassiveOwl
Nov 19 at 11:06

1

@danicheeta: Why? Reflection is necessary for this problem anyway.
– Flimzy
Nov 19 at 11:17

there is no way other than using reflect package, but I strongly suggest change your approach
– danicheeta
Nov 19 at 11:01

Can I ask why? The PDF package is Gofpdf, to generate a table it basically 'draws' individual cells and then stitches them together, meaning you have to get the individual cell width
– MassiveOwl
Nov 19 at 11:06

@danicheeta: Why? Reflection is necessary for this problem anyway.
– Flimzy
Nov 19 at 11:17

add a comment |

2 Answers
2

active

oldest

votes

up vote
5
down vote

accepted

reflect.TypeOf(Person{}).NumField()

 len(structs.Map(Person{}))

(you need to import "github.com/fatih/structs")

edited Nov 19 at 11:23

answered Nov 19 at 11:12

Ehsan.Saradar

41827

Nice, thanks for this - works great
– MassiveOwl
Nov 19 at 11:14

add a comment |

up vote
-1
down vote

The Object.getOwnPropertyNames(object) will return an array of property name for the given object

edited Nov 19 at 14:14

AmerllicA

2,90211033

answered Nov 19 at 11:04

Shiju

1533

Thanks, i'll try this
– MassiveOwl
Nov 19 at 11:06

2

This question is about Go.
– Flimzy
Nov 19 at 11:17

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
5
down vote

accepted

reflect.TypeOf(Person{}).NumField()

 len(structs.Map(Person{}))

(you need to import "github.com/fatih/structs")

edited Nov 19 at 11:23

answered Nov 19 at 11:12

Ehsan.Saradar

41827

Nice, thanks for this - works great
– MassiveOwl
Nov 19 at 11:14

add a comment |

up vote
5
down vote

accepted

reflect.TypeOf(Person{}).NumField()

 len(structs.Map(Person{}))

(you need to import "github.com/fatih/structs")

edited Nov 19 at 11:23

answered Nov 19 at 11:12

Ehsan.Saradar

41827

Nice, thanks for this - works great
– MassiveOwl
Nov 19 at 11:14

add a comment |

up vote
5
down vote

accepted

reflect.TypeOf(Person{}).NumField()

 len(structs.Map(Person{}))

(you need to import "github.com/fatih/structs")

edited Nov 19 at 11:23

answered Nov 19 at 11:12

Ehsan.Saradar

41827

reflect.TypeOf(Person{}).NumField()

 len(structs.Map(Person{}))

(you need to import "github.com/fatih/structs")

edited Nov 19 at 11:23

answered Nov 19 at 11:12

Ehsan.Saradar

41827

edited Nov 19 at 11:23

answered Nov 19 at 11:12

Ehsan.Saradar

41827

answered Nov 19 at 11:12

Ehsan.Saradar

41827

answered Nov 19 at 11:12

Ehsan.Saradar

41827

Nice, thanks for this - works great
– MassiveOwl
Nov 19 at 11:14

add a comment |

Nice, thanks for this - works great
– MassiveOwl
Nov 19 at 11:14

Nice, thanks for this - works great
– MassiveOwl
Nov 19 at 11:14

add a comment |

up vote
-1
down vote

The Object.getOwnPropertyNames(object) will return an array of property name for the given object

edited Nov 19 at 14:14

AmerllicA

2,90211033

answered Nov 19 at 11:04

Shiju

1533

Thanks, i'll try this
– MassiveOwl
Nov 19 at 11:06

2

This question is about Go.
– Flimzy
Nov 19 at 11:17

add a comment |

up vote
-1
down vote

The Object.getOwnPropertyNames(object) will return an array of property name for the given object

edited Nov 19 at 14:14

AmerllicA

2,90211033

answered Nov 19 at 11:04

Shiju

1533

Thanks, i'll try this
– MassiveOwl
Nov 19 at 11:06

2

This question is about Go.
– Flimzy
Nov 19 at 11:17

add a comment |

up vote
-1
down vote

The Object.getOwnPropertyNames(object) will return an array of property name for the given object

edited Nov 19 at 14:14

AmerllicA

2,90211033

answered Nov 19 at 11:04

Shiju

1533

The Object.getOwnPropertyNames(object) will return an array of property name for the given object

edited Nov 19 at 14:14

AmerllicA

2,90211033

answered Nov 19 at 11:04

Shiju

1533

edited Nov 19 at 14:14

AmerllicA

2,90211033

edited Nov 19 at 14:14

AmerllicA

2,90211033

edited Nov 19 at 14:14

AmerllicA

2,90211033

answered Nov 19 at 11:04

Shiju

1533

answered Nov 19 at 11:04

Shiju

1533

answered Nov 19 at 11:04

Shiju

1533

Thanks, i'll try this
– MassiveOwl
Nov 19 at 11:06

2

This question is about Go.
– Flimzy
Nov 19 at 11:17

add a comment |

Thanks, i'll try this
– MassiveOwl
Nov 19 at 11:06

2

This question is about Go.
– Flimzy
Nov 19 at 11:17

Thanks, i'll try this
– MassiveOwl
Nov 19 at 11:06

This question is about Go.
– Flimzy
Nov 19 at 11:17

add a comment |

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